Additional Cardholder

You weren't the primary. Poor you. You were the additional one, the one not liable for paying the monthly, the one with enough charm and cajole to convince Grandmama to add your name to her AmEx Black.

You are an authorized user, and any charges you make are simply concatenated onto the name of the original cardholder. So when you decide to buy those "vibrating health aids," you'd better hope that Grandmama thinks they're for your aching back.