GIFT CARD PAYMENT ON ACCOUNT DECLINED

I have been into the Game Store at Liberty Midlands Mall to make payment on my Game account. The cashier Yvonne Zondi would not take my incentive card for the payment. I asked for the Supervisor, Radhika, who also advised me the same. I asked for a copy of the terms and conditions where it states this, Radhika then tells me that i must call the RCS division. I have paid my Game account for the past 2 years with this card, if their policies change in any way, I as their customer should have been sent commmunication of this before the rule was implemented. As a result, my GAME account is not paid. AS LONG AS I MAKE PAYMENT, WHO GIVES GAME THE RIGHT TO DICTATE HOW I MAKE THE PAYMENT?????????????? PATHETHIC SERVICE FROM GAME AND THEIR EMPLOYEES....