I still cannot launch appl.???

I am totally lost. Not knowing I entered my MasterCard and it charged me for a game?? Or movie I did not want!! I thought I had to have a credit card to use I.Tunes. I cannot launch games for my family member? My husband and I thought it wanted our credit card on file to do anything on this apple I- pad. It is so frustrating. We are in the thought of returning this device to AT&T and call it a loss. Never again. It is only 4 weeks old February,10,2014 was date of purchase. We do not know why!! It gives us so many problems?and now a charge we did not even use any game???? Plz HELP!!! Mr.&Mrs. Jason Stoddard.....