Billed twice, and intrest being charged on a 12 months same as cash card.

I bought a Samsung Surrround Sound System from hhgregg. Co. Here in Daytona Beach. The first one was broken and I returned it to the store for a new one. When I got my first statement I saw I was charged over $1000.00 for a $400.00 item, I called the store and was told to call the credid card company and we would get it streightened out. Upon calling the credit card GE Money I was told to start a greivance proceedure and I was NOT TO MAKE A PAYMENT UNTILL THE INVESTIGATION was complete. Well I never got a greivance paper , howevwe I did get a statement for $57.00 and said my total debt was $428.20. Later in Oct, Black Friday we were shopping and wanted to purchase a Dyson Vacumme. I was told me card was blocked. The store and I both called GE Money and was told there was nothing they could , call the next day. When I called they said I didn't pay the $100.00 plus dollars I was asked for (the original payment request was for I think 125.00 which I was told not to pay) I told them the statement was for $57.00 which I paid. I also told them I never got another statement. He said one was sent out , I may not have gotten it yet but it was sent and I was asked for $115.00 because my pauyment was late. I said I paid what was asked for when asked , I thought the greivance was taken care of because the payment was back to $57.00 which was the amount agreed on. I had made the purchase on a 12 month same as cash deal, but the man I talked to said it note was acrueing intrest.
 I don't know whats going on now but I do know I cannot pay a bill I never got , nor should I pay twice the agreed amound for any reason...I need some help with this because the credit card company has things all screwed up . Can you help me to please get this account back on track since GE Money don't want to help..I have had good credit all my life and have never had this trouble before. I don't think they know what they are doing..Please Help , Gerald Mann, 2 Tropical Dr, Omrond Beach, Fl 32176. 386-441-9358