Exactly, check your credit bureau file if you are a joint account holder then that Debt should show on your credit report. If nothings on there then probably you are just an authorized user.
Ask the collector from RBC whose name(s) is/are on the account as the Account Holders.
Then ask him to give you a copy of the original credit card application and tell him once you get that you will settle the debt if you are a joint account holder.