Dissatisfied MTN customer

Worst service ever. Don't use their service. They messed up with my cancelllation request of a month to month Home router and I am in big trouble. They collected my device and sent it to MTN a month ago. They didn't follow the correct procedures while doing that. Now MTN is refusing to cancel the contract because they can't track the device. I lost the device and the sum card but still getting billed. When I go to the shop they just nod their head. Useless service.