No Signal most of the time.

I have a 4G tablet that I've had for just over a year now. in the beginning of my contract with MTN everything worked fine, but as time goes on, I hardly ever have a signal. most of the time it jumps between 4G, 3G & E and tells me "can't connect to network" I will be sitting in the same spot not moving when all this happens, including no signal, emergency calls only. as a paying customer this is unacceptable as I pay for services not being received, and I have projects that I need to do research on for my studies. MTN either has to sort out their connection issues or allow me to stop my contract, as they are in breach of contract, by not being able to supply me with the service that I am paying for. Regards Theo Esterhuizen