When you make FaceTime calls on iPhone and iPad, recipients see your Caller ID – an email or phone number. If this caller identity does not match what they expect, they do not know who is calling. Here's how to change your caller ID.
When you call someone using FaceTime, your caller ID is the number of the email or phone displayed on the screen. If your Apple ID is associated with many email addresses, it's even more likely that you're calling people whose identities are not recognized. This could leave unanswered calls or give an unexpected email address to someone else you would not want to receive.
Changing the Caller ID used when launching a new FaceTime call is a relatively simple process, and here's how.
To start, open the Settings application and press "FaceTime".
Note that e-mail addresses will only appear if you are logged in with your Apple ID. So make sure you are logged in and press the "Use your Apple FaceTime ID" button otherwise.
Then, tap the number or email address you want to use as the caller ID in the "Caller ID" section.
And that's all there is to it. Now, when you start a new FaceTime video or voice call, the phone number or email address you just selected will be the one used as the caller ID, which means that it will also be the one that your recipient will see.