damaged goods and bad service rendered

I got an offer to get two phones on contract from a cell c agents,which I accepted in november,then after just two months one of the handsets was no longer charging.I called the cell c call center and explained my problem.I was adviced to take the phone to a cell c store in brooklyn pretoria.I went there and the phone was booked for repairs.after a week I was called to come pick up the phone,but to my surprise the phone wasn't fixed and I was told its beyond repair.I then went home and called cell c call center and explained what had happened.I was tranfered from department to department to no avail as no one seemed to know who can help me.everytime I call them I end up staying on the phone for about 30 minutes to an hour.I've been paying for the phones ever since and I have never skipped even one installment but I'm just sitting home with a phone that's not usefull to me.I regret ever agreeing to take up this contract with cell c as their service is so bad.I should have stuck with my old service provider vodacom as they have never disappointed me this way,I'm even thinking of stopping the payments just scared they will blacklist me,but paying for something you are not using is bad