Mtn poor service

The service that I am receiving from mtn is absolutely poor. I upgraded my contract in July to an iPhone 7 the following month the back camera and flash stopped working. I sent my phone back to mtn to be sorted out. It's been almost 3 weeks now and I havent received any feedback with regards to it. So I decided to call the wonderboom junction branch that was assisting me only to find out that my phone has not been sorted out as yet. It is a real inconvenience to me. I paid my full installment for a device that I have not been using for almost 3 weeks and at the end of this month I will have to pay again which is really not fair! First they give me a faulty device and now I have to wait for only God knows how many more weeks to receive my device. Mtn service is really poor and disappointing!!!