Iphone 6 in for repairs for more than 2 months

I would like to lodge a complaint in regards to the service MTN has rendered to me recently. <br> I renewed my contract in April and got an Iphone 6 after 3 days I took the phone back because it was overheating, and I was given a new phone. 3 months down the line the rear camera was not working<br> The phone was taken in for repairs on the July 23rd till today I have not received my phone back. I was told at first that I need to pay R300 that they could not explain what was it all about since the phone is under warranty.<br> The second time they said It was because FIND MY PHONE app was activated and that I did not understand , how can an app on the phone can cause the camera to malfunction. <br> <br> I am fed-up with the bad service provided by MTN. Due to me not having a device for 2 months, I am unable to use the services I am paying for. I need this issue to be resolved immediately.<br>