This same question (with a slight difference) has been raised before but is now closed. I do not see any resolution for it however.
-Create new app says mobile phone required.
-Adding phone says is with another account and must be removed from other account first.
-Searching accounts by phone finds no such account.
-Place to add phone says cannot be in another account.
-Prior post had a solution of adding app via mobile device. Does not work for me. Still requires phone number.