Appauling service from MTN call centre agent

I have been experiencing Network problems for over three weeks. When I called MTN's call centre I was holding on the line for assistance for approximately 20 minutes. When an agent finally answered I was transfered to the Network Coverage department to Samantha Hield who simply told me they dont have network problems and that I should put my sim card in another phone. My question is how does that solve my problem as I'm using a brand new phone? I asked to speak to a supervisor and was told that the supervisor was not at work today. I then asked to speak to a Manager. Sorry we dont have a manager was Samantha's response. Really. I'm paying for a contract every month and I'm hardly able to use my phone. I sent an email two weeks ago so that I can get a cancellation quotation so that I can move to another cell phone provider seen that MTN is so pathetic. To date no response. Serioulsy!!! Can someone at MTN please stand up and take accountability for the terrible service.