Users can share the same Home or Work numbers on their user accounts. However, Cell phone (Mobile phone) numbers cannot be duplicated or shared on multiple user accounts for security reasons. If using and supplying a cell/mobile phone number, the number must be unique and not used on any other user account.
Why must my cell / mobile phone number be unique?
Cell / Mobile phone numbers are utilized to recover lost or forgotten credentials during the password reset process. In order for the system to be sure it is communicating only with the designated user during this process, the number must be unique, so the system is sure it has identified the correct and authorized user. These phone numbers are also used in order for us to prove account ownership and verify identity if we must send correspondence with a user. If more than one user shared a cell/mobile phone number, we would not be able to complete this verification in some situations. In a worst-case scenario, someone with malicious intent could register an account with your phone number and then claim to be you if we allowed multiple people to have the same cell / mobile phone numbers. We implement this strict policy to protect you, your identity, and your data for these security reasons.
What if the account is deactivated?
Deactivating a user account will not alleviate this conflict. A mobile phone number will continue to remain associated with the original user. It will be unusable by a new user account, even if a user account is deactivated or deleted.