Repair service

I got a new iphone5 in December 2014. At the end of May my phone was only 5months old. It gave me alot of problems and I had to send it in(I did not physically damage it). It came back 3weeks later, worked for one hour and gave the same problems again. Came back the second time with the same problems and I had to send it in for the THIRD time again and everytime I have to pay R150 for a sim swap. Mtn had my phone for a month and a half now and nothing is happening. Mtn had my phone in the time that it was still in the 6month warranty time where they should have just replaced my iphone. I have sent a few emails trying to get help from mtn but no reply. I am still without my phone for which we pay every month. I am really fed up with this very very poor service from mtn repairs and the mtn branch here in Beaufort West. Pathetic!