MTN router and service at Rustenburg Mall

It's now 3 months I have been coming to Rustenburg Mall for a router that is not working. Marco checked it twice and today I was helped by Darius. They are saying the problem is network coverage, My sister who I am staying with is using MTN on her phone and don't have a problem. They cannot exchange it or help me send my contact to MTN for a call back. They gave me a number that I never get through. I called the number before visiting the store, I was on hold for an hour. Imagine the airtime I spent. When I asked for cancelation, I have to pay R2200.00 after paying R1500.00 without getting service