wifi connection that never works.

Hi. My name is Nathan and I live on the bluff in durban. About 1 year ago we signed up with MTN wifi. Biggest mistake ever. I had personally been told MTN is the best provider to be on in my area. We have had very little to no connection since we got the contract. Now we are paying monthly for wifi which NEVER works at all anymore. Other than that we are supposed to get billed R310 pm and recently got billed R10000!! When asked why we got told we downloaded 60gigs in 1 hour. Which is impossible with the line speed in Sa. All I want is to cancel this contract as it is useless.. This is not the first time we got billed so high either. One month we had no Internet access at all and got billed 3000 rand. Which we only realised after checking bank statements a few months later. We then cancelled debit order and my father personally goes and pays 310 rand cash monthly. And still. The Internet does not work even 1 days out of the month.. HELP!!