no internet service

I am a contract subscriber for the internet, but for the past couple of months I have no internet service what so ever. I cannot open web pages as MTN's internet servicer is not capable of doing so. The only response I get is Page cannot b e displayed or the servjce is so slow when I do manage to open a page it sometimes take up to 30 minutes to download something if it ever succeeds. l lodge several complains at the stores and was always told that there is a problem and that they are working on it , but the problem still persists. This is quite unacceptable as I am now paying for a servjce I don't get.