MTN misrepresent contract renewal

During February I was contacted to renew my cell contract. I was promised that the contract in terms of minutes and data would remain unchanged. 6 weeks later when the airtime and data was provided, there were no data and the airtime was changed. On top of that accumulated airtime from the previous contract was removed. I have now been struggling since early April to try and get this resolved, but MTN is not interested in my problem.