LACK OF CUSTOMER SERVCE, MTN

I am absolutely horrified at the service by MTN. I have been a loyal customer for a few years. I opened a contract for my partner on my name about two years ago and when it came to upgrade time, we thought, why not? Well. Within a month, the phone was broken with a hardware issue that we could not fix. We did everything MTN told us to do, and handed it back to the George Mall branch with everything they said they needed. I got the customer returns form that said that valid proof of purchase was attached. Over a week later, I had heard nothing, so I called to find out what was happening with the phone. I was then told that the phone could not be replaced, BECAUSE THERE WAS NO VALID PROOF OF PURCHASE ATTACHED, even though, the customer returns document said that there was valid proof of purchase attached!! I have tried calling, my boyfriend has tried, his sister has tried and we are getting absolutely nowhere. I will be going forward to canceling the contract, MTN has lost a loyal customer!