cell c try to rip me off

I bought my I phone 4s last year at cell c shop in Ilanga mall. My monthly contract instalment is R290. Everything was ok until few weeks ago.Suddenly the phone did not want charged at all.Then on the 28 of last month I took it back to cell c ilanga mall where they book it to their repair centre.You won't believe this, but on 04/06 I receive an sms that there is quotation of R5472.Upon contacting this not so friendly lady at cell c repair centre. She told me that I have to pay that amount because they are offering me a brand new phone. Then I told her I don't want a new phone, I just want my old phone fixed. Then she said they are unable to fix it because it does it want to switch on. Then I told her it won't switch on because the battery is flat (since it does not want to charge) .According to my understanding if the repair guys are unable to fix the problem, I think that's cell c's problem not mine. It's not customer's fault that the phone does not want to charge, but a factory's fault. To me, this is a complete *******. My contract expires at the end of Janry next year, and based on the service that I receive from cell c I doubt if I will ever renew it again.John ***