To forward calls from one mobile to another right now, dial 21[destination number]# and press call. That single string activates unconditional call forwarding at the network level, meaning every incoming call redirects immediately, even if your phone is switched off.
Two routes get you there:
- GSM/MMI star codes (network-level, works even when the handset is off or out of battery): dial the code directly from your dialler and press call.
- Handset settings (iPhone: Settings → Phone → Call Forwarding; Android: Phone app → Settings → Call forwarding): quicker for a tap-based toggle when your phone is on and the menu is available.
To verify it worked, dial *#21# from a second phone or ask someone to ring your original number. If the call lands on the destination mobile, forwarding is live.
Pro Tip: Always test from a separate phone rather than relying on the on-screen confirmation. The handset can show “forwarding active” before the network has actually accepted the rule, so a real test call is the only reliable check.
EE, O2, Vodafone, and Three all support these GSM/MMI star codes as part of the standard GSM supplementary services framework.
Key takeaways
Forwarding calls from one mobile to another in the UK takes under a minute using 21[number]#, but the method you choose and the format you enter the number in determine whether it actually works.
| Point | Details |
|---|---|
| Fastest activation | Dial 21[full number]# and press call to activate unconditional forwarding immediately. |
| Handset paths | iPhone: Settings → Phone → Call Forwarding; Android: Phone app → Settings → Call forwarding. |
| Test every time | Call your original number from a second phone — on-screen confirmation alone can be misleading. |
| Cost caveat | Forwarded calls are typically charged as outgoing calls; PAYG and roaming users should check plan terms first. |
| Master cancel | Dial ##002# to clear all active forwarding rules at once. |
Table of Contents
- How do you forward calls from mobile to mobile using star codes?
- How do you set up call forwarding on an iPhone?
- How do you set up call forwarding on Android?
- What are the UK carrier rules for EE, O2, Vodafone, and Three?
- How do you cancel call forwarding and check what is active?
- What does call forwarding cost on PAYG and when roaming?
- What should you do when call forwarding is not working?
- Best practices for reliable call forwarding
- Network codes vs handset settings: which should you use?
- Sources
- FAQ
How do you forward calls from mobile to mobile using star codes?
Star codes (also called MMI codes) are the most reliable way to set up mobile call forwarding because they communicate directly with the carrier’s network switch, bypassing the handset entirely. That matters when the phone menu is missing, the device is broken, or you need the forward to survive a flat battery.
The standard format is: [service code][destination number]# then press call.
For UK numbers, enter the destination with the leading zero (e.g. 07700 900123) or in +44 format (+447700900123). Dropping the leading zero without adding +44 is the single most common reason a forward silently fails, so double-check the format before you dial.
The universal cancel ##002# clears every stored divert rule in one go, which is the safest way to reset if you are unsure what rules are currently active. Connection Technologies confirms that ##002# clears all diverts across UK networks.
One practical note: setting unconditional forwarding (21) overrides any conditional rules you have already set. If you need “no answer” or “busy” behaviour, clear unconditional first with ##21#, then apply the conditional code.
Pro Tip: Save your most-used MMI codes as contacts on your phone (e.g. name one “Divert ON” and another “Divert OFF”). Tapping a contact to dial is faster than typing the string from scratch every time.
How do you set up call forwarding on an iPhone?
Apple’s built-in path is the easiest option for unconditional forwarding when your iPhone is working normally. According to Apple Support, the route is:
- Open Settings.
- Tap Phone.
- Tap Call Forwarding.
- Toggle Call Forwarding on.
- Tap Forward To and enter the destination number.
- Return to the Call Forwarding screen to confirm the number is saved.
A small phone icon appears in the status bar at the top of the screen when unconditional forwarding is active. That is your visual confirmation.
The key limitation: the iPhone Settings menu controls unconditional forwarding only. For conditional forwards (busy, no answer, unreachable), you need to use the MMI star codes from the dialler. This catches a lot of people out, because the Settings path looks like it covers everything when it does not.
To cancel from the handset, go back to Settings → Phone → Call Forwarding and toggle it off. To check status without opening Settings, dial *#21# from the dialler.
Pro Tip: After toggling forwarding on, immediately call your original number from a second phone. The status bar icon can appear before the network confirms the rule, so a live test call is the definitive check.
How do you set up call forwarding on Android?
Android exposes more forwarding options than iPhone by default, including the conditional states, though the exact menu location shifts depending on the manufacturer.
The standard path on most Android devices:
- Open the Phone app.
- Tap the three-dot menu (top right) or the kebab menu.
- Tap Settings.
- Tap Calls or Supplementary services.
- Tap Call forwarding.
- Select the forwarding type: Always forward, When busy, When unanswered, or When unreachable.
- Enter the destination number and tap Enable or Turn on.
Android menus typically show all four forwarding states in one place, which is more transparent than the iPhone Settings path. You can set “when unanswered” directly without touching a star code.
- Samsung One UI: the path is Phone → More options → Settings → Supplementary services → Call forwarding.
- Xiaomi / MIUI: Phone → Settings → Call settings → Call forwarding.
- If the menu is missing entirely: use the MMI star codes or your carrier’s app. A missing menu usually means the carrier has not provisioned supplementary services on that SIM, not that the feature is unavailable.
For dual-SIM phones, select the correct SIM line before entering the forwarding menu. Each SIM holds its own forwarding rules independently, so setting a forward on SIM 1 does nothing for calls arriving on SIM 2.
Pro Tip: If you have recently swapped a SIM into a second-hand handset and the call forwarding menu is greyed out, the issue is almost always carrier provisioning rather than a handset fault. Call your carrier and ask them to enable supplementary services on the account.
What are the UK carrier rules for EE, O2, Vodafone, and Three?
The MMI star codes are part of the GSM standard, so they work across EE, O2, Vodafone, and Three on pay-monthly contracts. PAYG is where things get more complicated.
- EE: PAYG customers can typically forward to voicemail but forwarding to another mobile number may be restricted. Check EE’s support pages for your specific tariff.
- O2: PAYG forwarding to external numbers is available on some tariffs but not all. O2’s help centre lists the current restrictions by plan.
- Vodafone: Most PAYG plans support forwarding to voicemail only. Pay-monthly customers have full access. See Vodafone support for current terms.
- Three: Forwarding is generally available on pay-monthly; PAYG restrictions apply. Three’s support pages carry the latest detail.
Voicemail short codes are commonly used as forwarding destinations when you want missed calls to go to your carrier’s voicemail rather than another handset. These codes differ by network and should be confirmed directly with your carrier, as they can change.
Forwarded calls are typically treated as outgoing calls from your original number. If your plan includes unlimited minutes, those calls usually draw from that allowance. On PAYG, each forwarded call can cost per minute, which adds up quickly if you leave unconditional forwarding running.
Pro Tip: Before setting up long-term forwarding on a PAYG SIM, make a short test call to the destination and check your balance before and after. That tells you exactly what each forwarded minute costs on your specific tariff.
How do you cancel call forwarding and check what is active?
Cancelling a single rule and cancelling everything are two different operations. Use the specific cancel code when you want to remove one type of divert and leave others in place.
To cancel individual diverts:
- Unconditional: ##21#
- Busy: ##67#
- No answer: ##61#
- Unreachable: ##62#
To cancel everything at once: dial ##002# and press call.
To check what is currently active:
- Dial *#21# to check unconditional forwarding status.
- Dial *#61# for no-answer status.
- Dial *#67# for busy status.
- Dial *#62# for unreachable status.
Your carrier will typically return an on-screen message showing the destination number if a rule is active, or “not active” if it is not. After cancelling, dial the check-status code again to confirm the rule is gone, then make a test call from a second phone to verify incoming calls reach you normally.
If a cancel code appears to succeed but forwarding continues, the handset menu and the network may be out of sync. Trust the star-code status check over the handset display, and if the problem persists, dial ##002# to clear everything and start fresh.
What does call forwarding cost on PAYG and when roaming?
Billing behaviour is the part most guides skip over, and it is where unexpected charges come from.
Forwarded calls are commonly charged as outgoing calls from your original number, as confirmed by fonea’s UK call divert guide. On an unlimited pay-monthly plan, those outgoing minutes are usually included. On PAYG, each forwarded call can cost per minute at your standard outgoing rate, so leaving unconditional forwarding running on a PAYG SIM is an easy way to drain credit.
- PAYG: some networks restrict forwarding to voicemail only; others allow forwarding to any UK mobile but charge per minute. Rates vary by carrier and tariff.
- Roaming: forwarding a UK mobile to an overseas number while abroad creates a double charge in many cases. You pay to receive the call internationally, and then pay again to forward it outward. This can be significant.
- International destinations: forwarding to a non-UK number from a UK SIM is treated as an international outgoing call and billed accordingly.
A short cost-check routine before committing to long-term forwarding:
- Call your carrier’s customer service line and ask specifically whether forwarding to a mobile is included in your plan.
- Check the plan’s terms for “supplementary services” or “call divert” billing.
- Run a test forward to a local UK number and check your usage log or balance immediately after.
- If you are travelling, consider cancelling forwarding before departure and using a VoIP app instead.
For more on forwarding costs and number choices, the type of destination number also affects what callers pay to reach you.
What should you do when call forwarding is not working?
Most forwarding failures come down to one of four causes: wrong number format, carrier provisioning, a conflicting unconditional rule, or a handset menu that is out of sync with the network.
Work through this in order:
- Check the destination number format. Enter the full number with the leading zero (07700 900123) or in +44 format. A missing digit or wrong prefix is the most common cause of silent failures, as noted in this practical forwarding guide.
- Check status with a star code. Dial *#21# to see what the network actually has stored. If it shows a different number or “not active”, the handset confirmation was misleading.
- Cancel and reapply. Dial ##002# to clear all rules, then re-enter the forward using the MMI code rather than the handset menu.
- Test from a separate phone. Call your original number from a different device. Do not rely on the on-screen status alone.
- Contact your carrier if the above steps fail. Ask them to confirm supplementary services are provisioned on your account.
Additional checks for specific situations:
- Dual-SIM phones: confirm you are setting the forward on the correct SIM line.
- Refurbished handsets: a previous owner may have left forwarding rules active. Dial ##002# as a first step on any second-hand device.
- Forwarding loops: if forwarded calls go straight to voicemail unexpectedly, check that the destination number does not itself have forwarding active back to the original number.
- Missing handset menu: use MMI codes directly. The menu being absent does not mean the feature is unavailable.
Best practices for reliable call forwarding
A few habits make the difference between forwarding that works when you need it and one that quietly misfires.
- Choose the right trigger. Unconditional (21) redirects every call, including ones you could have answered. Use conditional forwards (busy, no answer) when you only want calls to divert under specific conditions.
- Enter the destination in the exact format. Leading zero or +44, no spaces, no brackets. Test the number by calling it directly before setting it as a forward destination.
- Test from another phone every time. Set the forward, then immediately call your original number from a different device to confirm it lands where expected.
- Document what you set. Note the destination number and the divert type. It is easy to forget an active forward, especially on a work SIM.
- Cancel when you are done. Dial ##002# when the forward is no longer needed. Leaving unconditional forwarding running on a PAYG SIM costs money; leaving it running on any SIM means you miss calls you did not intend to redirect.
- Review before travel. Check forwarding status with *#21# before leaving the UK. An active forward to a UK number while roaming can generate unexpected charges.
For business users managing multiple lines, a call forwarding checklist helps keep rules consistent across the team.
Pro Tip: Forward to a number that will reliably answer. Forwarding to a line that is itself busy, forwarding elsewhere, or going to an unmonitored voicemail box defeats the purpose entirely.
Network codes vs handset settings: which should you use?
The handset toggle is convenient. The star code is reliable. Those two things are not always the same.
When a phone is working normally and you need a quick unconditional forward for an hour, the iPhone Settings path or the Android call forwarding menu is perfectly fine. It takes ten seconds and you can see the status bar icon. For that use case, the extra step of typing a star code adds nothing.
The calculation changes the moment the situation gets complicated. A device going in for repair, a SIM being redeployed to a different handset, a forward that needs to survive the phone being switched off: all of these call for the network-level MMI code. The rule lives on the carrier’s switch, not on the handset, so it persists regardless of what happens to the device.
There is also a subtler reason to prefer star codes for anything beyond a simple unconditional forward. Handset menus can fall out of sync with what the network actually has stored. The phone shows “forwarding active” while the network has already timed out the rule, or vice versa. The star-code status check (*#21#) always reflects the network’s actual state, which is the only state that matters.
For anyone managing forwarding across multiple numbers or thinking about longer-term call routing, remote call forwarding for UK businesses covers the more structured approach.
Sources
- Apple Support — iPhone: Use call forwarding
- Call Divert iPhone UK 2026: All Networks + MMI Codes | CT
FAQ
Can you forward mobile calls to another mobile in the UK?
Yes. Dial 21[destination mobile number]# from your handset and press call to redirect all incoming calls to another mobile. Most UK pay-monthly contracts support this; PAYG restrictions vary by carrier.
What do you dial to activate call forwarding?
For unconditional forwarding, dial 21[full number including leading zero]# and press call. For conditional types, use 61 (no answer), 67 (busy), or 62 (unreachable) in the same format.
How do I forward calls from my mobile to another mobile on iPhone?
Go to Settings → Phone → Call Forwarding, toggle it on, and enter the destination number. This covers unconditional forwarding only; use MMI star codes for conditional forwards such as “when busy” or “no answer.”
How do I cancel all call forwarding at once?
Dial ##002# and press call. This clears every active forwarding rule stored on the network, regardless of which type was set or how it was activated.
