Old phone number associated with iMessage on iPhone

[calski]

I have just got a new iPhone 11 on a contract with O2. When the phone arrived, I set it up using a temporary phone number (ending -410) and – unintentionally – managed to add this temporary phone number to iMessages for 'Send & Receive'.

Yesterday, O2 ported over my old O2 Business phone number (ending -227) to the SIM card in the device, deactivating the temporary number (-410) and replacing it with my old (and now current) phone number (-227). So -227 is the number that I want in my phone and is active; -410 is the temporary number and is no longer active (I want it gone). I can't re-insert a different SIM card with the old number to remove it that way, as the number that I want (-227) has overwritten the number on the original temporary SIM card (-410).

The problem is that my phone now seems to be linked to a number that no longer exists (-410). When I rang this number, to check that the port worked out, it cannot be recognised, so it's definitely not active any more. But whenever I text anybody with an iPhone, it comes up on their phone as being from the number ending -410, instead of my actual number -227.

I've tried signing out of iMessage and FaceTime on all of my devices; I've tried resetting my Apple password, but that number still remains.

Any suggestions?

[MI5 · Accepted solution]

@calski 

Go to Settings >phone >my number. 
Edit to your number and save then reboot phone. 

[calski]

Problem solved. Many thanks. Didn't even know that setting existed...

Seems a bit odd that it doesn't just pull the number from the SIM card as you could surely just enter any number you like?!

[MI5]

It's because your sim has the wrong number on it @calski and o2 don't push the ported number to the sim. 
You could enter any number but iMessage and FaceTime wouldn't activate unless it was correct.