Breach of contract between MTN network supplier and customer

Hello,my name is Bridgette Radebe I'm sending this email on behalf of my mother Roseline Radebe,she took a airtime contract of R29 with Mtn then they increased the amount to R55.00 without her consent and they told her that she can cancel it anytime because there was no written agreement only a verbal one over the phone,she took the contract this year june then last week when we called them trying to cancel the contract we where given the run around and she got an email from them saying she will be able to cancel the contract june of 2017 and that's not what they agreed on can hello peter please intervene and help her terminate the contract.