I am having a similar problem. In my case, I had a Secondary user on my account which I deleted. Now, when I try to add the phone number that was associated with that Secondary user to my account's Primary user information, I get the exact same message as babygirl357159 .
Obviously, I cannot remove the number from the Secondary user because it is gone from my account completely (since I deleted it). Thanks in advance for any help with this.
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