FaceTime & iMessage mobile number not updating

At the end of last year I was in Finland. I purchased a temporary SIM card, inserted it into my iPhone and when asked if I want to use the new number for FaceTime/iMessage I said yes. I thought this would simply add the number to my existing AppleID contact options. The number worked fine with FaceTime & iMessage while in Finland.

I have now been back home for about 2 months with my original SIM card in my phone, however FaceTime & iMessage still have the Finnish number saved. They are unable to verify it (duh) and when I remove & add my current SIM card nothing happens (ie. it doesn't ask me if I want to change my number) and I have no option to "force" a verification or association with my actual SIM card & number here back at home.

I have signed out and in of my AppleID on the phone, I have ensured the number I use at home is saved to my AppleID (where it even says that the number is verified and should be available to FaceTime and iMessage) but no luck. I have also tried every possible combination of enabling and disabling the FaceTime and iMessage apps on my phone, doing this before and after and while I am not signed into my AppleID on the phone.

This is an issue because some of my contacts don't have (& shouldn't have) the email address linked to my AppleID and thus can't contact me via the Apple ecosystem.

Help please! Digital hugs for payment.

Thank you,

Marcus