Why won't my call forwarding code work?

If you dialled **61*number**20# and it was rejected, try **61*number# with no ring time on the end. The custom ring time is an optional part of the code and it is the part networks most often refuse — some accept only certain values, some only in five-second steps, and some ignore it entirely.

You lose nothing by dropping it. The divert still works; the network just uses its own default delay before forwarding, which on most UK networks is around 20 seconds anyway.

If that fixes it, the divert was never the problem. This is the single most common cause of "the code does not work" and it is worth trying before anything else.

Keypad codes and the phone's own call-forwarding menu set the same network rule by different routes. If one is refused, the other often is not.

On Android: the Phone app, then the three-dot menu, then Settings, then Calls, then Call forwarding, then When unanswered. A dual-SIM handset asks which SIM before showing the rules. Some manufacturers put this under Supplementary services or Calling accounts instead.

On iPhone: Settings, then Apps, then Phone, then Call Forwarding — but note that iOS only exposes forwarding for all calls, not the no-answer condition. On an iPhone the keypad code is usually the only way to set a conditional divert, which makes the ring-time fix above the important one.

On a dual-SIM handset, check you set the rule against the right line. Setting it on the wrong SIM is a very easy mistake to make and produces exactly the symptom of a rule that saved fine and does nothing.

Some plans allow diverting to voicemail but not to an external number. This is most common on pay-as-you-go and on MVNOs — the smaller networks that run on someone else's infrastructure — where the host network supports forwarding but the reseller has not enabled it on every tariff.

The tell is a code that is accepted for voicemail and refused for an ordinary number, or one that appears to save and then does nothing on a real call. If you see that, ring your network and ask specifically whether call divert to an external UK number is provisioned on your line. That phrasing matters: ask about "call divert provisioning", not "call forwarding", or you will be walked through the handset menu again.

Business and pay-monthly lines are generally the least restricted. If you have a second line on one of the four main networks, testing there tells you quickly whether the problem is your plan or your phone.

Check what the line actually thinks is set with *#61#. A confirmation tone means your handset accepted the code, not that the network applied it, and those are different things.

Look for an all-calls divert underneath. If **21* is set to voicemail from some earlier attempt, it takes effect before your phone ever rings and your no-answer rule never gets a chance to run. *#21# will show it, and ##002# clears everything so you can start from a known state.

Check the destination number format. Use the full national number including the leading 0. Some networks also accept +44 form; few accept a shortened or spaced version.

If it worked and then stopped, look for what changed. A SIM swap, a tariff change and occasionally a major OS update all cause networks to re-provision the line, which puts the voicemail destination back and silently removes yours.