Shocking MTN WiFi connectivity.

Been loyal MTN customers for nearly 30 years. Customer service is at its lowest, absolutely shocking. Our WiFi connectivity is almost zero, on/off constantly, ie no connection. We were told by MTN that WiFi connectivity in our area was outstanding, "no problem", had to sign two-year contract, we've kept our side of the bargain by paying regularly, yet MTN doesn't perform at all!! We're paying for an almost non existent service. Now we're stuck with a contract with no service or reward. I've reported this problem to MTN repeatedly, just promises from them, but nothing changes!!! To say we're frustrated us an understatement!! Can we cancel our contract based on MTN's lack of service delivery??