MTN is the worst

So I app**** for a phone contract and got a SIM card instead as it was conditionally approved. This is a data sim for r159 a month I have called in twice as they have given a spend limit to use for r350 which I don’t want to use and I cancelled this services twice. My bill for the 7th is already r183 which I can’t understand why ? I am only supposed to pay r159. From day one I have had a problem with this network. I would like to cancel my subscription immediately