Hello AshleyMcCane,
We see you're looking to remove a phone number from your Apple ID, and we'd be happy to help.
There's a helpful note on that topic here: Add or remove your phone number in Messages or FaceTime
If you scroll down to the "Remove your phone number" section, it'll note the following: "If the phone number that you want to remove belongs to an iPhone that you can't access, change your Apple ID password. This removes all phone numbers from your iPad, iPod touch, and Mac. Calls or messages for the removed numbers won't appear on those devices anymore."
To change your Apple ID's password, so that it'll remove the number, you can find help for that here: Change your Apple ID password
Cheers.