I don't believe you are liable

to this credit card debts.

It's the primary card holder's responsibility. Usually they don't even need additional card holder's SSN. To make sure, ask for a copy of term and condition from the bank.

Of course they would say you are liable because you are their only hope.

But they also have the right to call if they can't collect their money.

You can either change your phone number or install a caller ID and do not pickup their phone call ;-)