MTN: Contract cancellation nighmare & Worst service provider

I took a cellphone contract in December 2019 from MTN for R229 and yet they have been overcharging me every month since then. In December my bill reflected a higher amount than the preinvoiced amount which is the reflection of the contract i entered. I went instore at the Northgate Mtn Shop and the agent who assisted me when i took out the contract said the amount i will be billed is R229 and not R329. I asked that my contract be cancelled on 20 December 2019, MTN responded via an email and stated that a consultant from their cancellation department would call me back in 24-48 hours. I never received the call. In January i travelled and as a result i couldnt go into their shop to get this resolved nor call them. Despite having asked Mtn to cancel my contract to no avail i continued to pay via EFT while out of the country so that i do not ***** my credit record. To my surprise when i opened my statement in April 2020 it had an arreas balance because Mtn had been charging me R329 instead of the R229 per month that i have been faithfully paying. I asked them to investigate this matter on 20 April 2020 by reviewing the contract and the preinvoice that i signed instore, it took them more than a month to revert to me after sending endless emails. On 20 April i also sent customer retentions at mtn an email requesting to cancel my contracts with them and since then i.have not received a response. The response to the discrepancy in the amounts was sent via an email that had an attachment that was supposedly the signed contract however the attachment also didnt open. I sent Mtn an email stating that i cannot open the attachment however i have not received any communication from them.

This is the worst service i have ever received from a service provider. So easy to get the contract but impossible to get out of it. I dont want these contracts anymore and need them cancelled with immediate effect however being out of the country makes it difficult to communicate with Mtn as i cannot call their customer care and can only email them. Despite the law stating that one cannot be forced to be party to a contract when they do not want to anymore it seems Mtn still uses other means such as non-responsiveness to force people to stay in contracts. What other remedies are available to hold them accountable and not be forced to stay in contracts when one doesnt want to anymore?