No Network Coverage

Since a few month my network coverage at home is on edge. Due to the fact that I had coverage before it is unacceptable and nobody at MTN can explain to me why. I tried several other phones and the coverage is still the same. So it is not my cellphone either. I am working a lot from home and that clients can't reach me or hear me properly is a huge problem. The only option I have is to cancel my contract which is actually not my fault. I was sitting yesterday 2 hours at the MTN shop Waterstone Mall to find out how much it will cost me to cancel my contract. To cancel I have to pay R1500. I am not prepared to pay such a fee due to the fact that the coverage in my area changed.