MTN-THE MOST USELESS CELLPHONE PROVIDER EVER

I am on contract with mtn, I got my phone in August 2013<br> My phone is still under warranty and still under mtn. suddenly my phone doesn't charge and I called MTN centurion to ask what I should bring for repairs<br> I was advised to bring in charger and device and ID<br> I did just that and when I got there, they refused to take in m y phone saying they need a proof of purchase<br> Why do they need proof of purchase if I am on contract with them and they have deduct money from my account every month <br> I don't have proof of purchase, because I got the phone in 2013 and in between I moved places<br> My friend had the same issue but her phone is under VODACOM, they had no issue fixing her phone, all they wanted was a her original id as they had all proof in their systems<br> I will switch to Vodacom, mtn is useless. No assistance whatsoever<br>