iMessage, FaceTime and Mobile Calls UK Based O2 Provider

About 6 weeks ago we changed provider from Vodafone to O2 since then we have not been able to use our mobiles for iMessages, FaceTime or receiving calls apart from calling each other.

We appear to receive calls from other O2 mobiles although this has been limited as this was from the O2 branch. We can use WhatsApp for messages and calls.

I have been over all the details with Apple, re-set network settings on number of occasions. They have checked both mobiles everything seems to be working correctly.

I have been over this with O2 on a number of occasions and still nothing works.

Verification of both mobile numbers fails on every attempt with either an error occurred or similar

Any ideas/solutions we are at our Witt’s end with this

iPhone 14 Pro Max.