Infuriated by the service

My sister took out a credit card from Game stores and was told that she will be paying a certain amount per month. She took a treatmill at the store using the funds on the credit card. Game stores didnt waste time in taking her money, 1st month into it her debit was almost double what was initially agreed upon. And every month after that the instalment has been flactuating and going up, worst of all no one bothered to explain how and why this is hapenning. She called the call centre for help and the consultant couldnt help, promised to call her back...and that was 2 days ago, no call!!! She called again today and was put on hold for an entire 30 minutes!!!Tell me Game stores, DOES CUSTOMER SERVICE MEAN NOTHING TO YOU???