How can I make FaceTime work after changing my contact number?

Re: "Hello i whant to chang my contact no.then my face time not work.how can i use my face time"

If you have changed the phone number in your Apple Account:

Try signing out of FaceTime, (or exiting the app) that is still using the old number.

Sign back in to FaceTime with your Apple Account ID and password.

or

If needed: Restart the computer or device you use for FaceTime

Else: If you haven't changed the phone number in your Apple Account:

Log-in to your Apple Account online: https://account.apple.com/:

In the security section:

add the new phone number first, to allow deleting of the old one.

Allow 24 hours for the change to update wherever the number is used for Apple