iMessage not working after number port

Have upgraded phone from iPhone 7 to XR.

have had my number ported across as have changed networks.

I can make and receive phone calls using the correct number(my original one that was ported across)

WhatsApp is working

SMS is working

imessages are NOT working. They are using the new number that was given with the phone.

I have tried turning iMessages and FaceTime on and off but it hasn’t worked

also turning phone on and off doesn’t work.

haven’t got chance to go to Apple store for 2 days so if anyone could help that would be great!!!