SH400.70.3: This Mobile Phone Number already exists. -pease fix to allow multiple accounts to phone#

I keep getting a notice that my account is not complete, please enter a mobile phone number.   I comply and you tell me that "SH400.70.3: This Mobile Phone Number already exists."  which correct.   The phone is associated to another account and I would like to use the same phone number to associate to my primary account.

Please fix to allow the phone number to be entered.

1.  I will stop getting annoying notifications every time I log into my account that is it not complete.  It would be if you saved my mobile phone number as entered.

2.  I can enable multi-factor authentication.   - You are preventing me from implementing and securing my account, and/or multiple accounts.

3.  This problem has been a reoccurring theme for myself and many other users at comcast - please fix and thereby improving security for your customers.    I reported this problem over 2 years ago, and so have many other people.   For 2 years I get the annoying "your account is not complete" message.    It would be if you saved my mobile phone number.   - Fix the problem.

Telling me I have to have a separate mobile phone number per account is a non-answer, and a rediculous answer - allow a mobile phone number to be associated to accounts.    Or how about providing me with multiple free mobile phones and phone numbers to support.