Trapped by service provider

I have joined cell c on the 3rd of November through the contract buy out scheme. I had endless issues from day one with regards to signal/reception. The staff where all helpfull but turned out to be empty promises as I had to follow up myself EVERY DAY to get results. A technician eventually came out to test signal/reception, he reported that there were none. When I followed up afterwards the person who handled my query informed me that theres nothing that they can do for me at this point in time and that they are willing to cancel the contract WITHOUT ANY PENALTIES. I arranged to go all the way out to head office (for the 5th time) to hand in the handset and finalise everything. All of a sudden the person who handled my query said I will only have to sign a debit order for the amount of R10 000 for the buy out card that we used to PAY THE PREVIOUS SERVICE PROVIDER to cancel that contract. He then said that cell c wants it all back in ONE INSTALLMENT. Now because I do not agree with that in the first place and that they will not even except installments, I AM TRAPPED. Even after all of this they still cannot resolve the problem and I have to endure the next 24 months paying top $