Temporary number issue on iPhone 13 after porting

[Tezx]

Recently Ported over my phone number of some 25 years or more to O2 from Virgin Media

My O2 account shows my Ported number, however, I keep getting messages that tell me this number will be used for imessage etc

When i go into settings the temporary Sim number allocated during the porting phase is still showing as being registered to my phone. No matter what i do, restart, change settings, etc etc, I cannot change this number

Further more my phone tells me that I have only 26 days left of my Original number left

Anyone any ideas on how to resolve? Phone contact is about as much use as a Chocolate Fireguard, Online Chat just isn't working for some reason, cannot find any useful info on the situation anywhere on the O2 site

I cannot afford to lose this original number, its associated with 25+ years of work colleagues, friends, family, websites, business associates etc

Thanks in advance for any help 

[MI5 · Accepted solution]

@Tezx 

Start off by resetting your network settings.

[Tezx]

Brilliant, thanks MI5 that appears to have solved the issue. 
cheers 👍 

[MI5]

You're welcome