Hey Flick2017,
The telephone number associated with iMessage and FaceTime has to be one that is active on the device, and should mirror the number you see at Settings > Phone > My Number. We know that some carriers will give you a temporary number to use when you switch to allow time to port your number from the previous carrier, so we encourage you to check here and see if it’s displaying the correct number. If it isn't, reach out to your new carrier to check on the status of your port.
If it is, check to see if you can make/receive calls and SMS messages using your number. You’ll need to be able to successfully send a text message using that number for it to fully activate, and it can take up to 24 hours after everything is fully provisioned for it to register with iMessage and FaceTime.
These articles explain in more detail:
If you’re showing the correct number at “My Number” and you’ve toggled iMessage off and back on (without touching it again) for 24 hours, let us know. We want to make sure you’re able to keep in touch!
Best regards.