MTN ***** and incompetence

Im fed up with MTN incompetence. In January i took a contract on special for 80gig data for 24 months at R299.00. But now every month they charge me R301. Iv sent numerous mails querying how and why has this fee change from my contract without notification or consent. I have not received any communication from their side. I will be escalating this to the ombudsman and cancelling my contract and leave them all together and move to another service provider