I am the parent and my son will be 18 next month. I have bought a $10 credit on amazon and put it into my parental account thinking I can use it there to give to my son. On my parental account is a gamer tag that my son has never used and his gamer tag is a different one. So I called XBox support and she told me to add his account as a family member so he can use the credits of $10 in the account. We did that but he cannot use it. What do we do so he can use it? Please help!!