defect device

Received the mobi cell device in July , since july I have not had the pleasure of using the device , however cell c debits my cheque account every month , the device has gone in for repairs for the second time now, on speaking to Angeline I expressed my dissatisfaction and also requested for a complete new device as obviously the device handed to me is a defect one this was on the 14.10.2015 not withstanding that this is on going since August she sent me confirmation of our conversation and I Quote\Please book the device in and I will escalate to management to swap the device or process a CPA credit."since our last conversation I have been chasing to get this resolved only to receive confirmation on the 26.10 quote \""Please be advised that the credit been declined the device is being repaired\"" how many times must this device be repaired and each time I have to take the device to a cell c store "