I had the same problem. Even though I had a total of 3 phone numbers confirmed in my account, it would not display an option to "Remove" what was (10 years ago) my "primary" home phone number (which was disconnected long ago). I already had confirmed a new "primary mobile number" but that did not make a difference-- the option to "Remove" was not present for the number I wanted to remove.
I eventually just had to go to "help" and (surprisingly) when I entered "unable to remove phone number" in response to the chat bot's inquiry about my issue, it displayed all 3 phone numbers I'd confirmed previously, asked me which one I wanted to remove, asked for confirmation of the number I wanted to remove, and the bot removed it instantaneously.
I guess bots aren't all bad. Sometimes they actually work 🙂
