MTN absolutely useless

On 19 October 2019 I took out a data contract with MTN. This was due to upgrade or cancel on 19 October 2021. You have to contact MTN via 135 to cancel a contract. What an absolute nightmare as they do not answer their calls on 135. I have send various emails to the retentions department and made contact via Facebook and Messenger as well. Promise after promise to cancel my contract and in the meantime I have to pay for this contract as it has been linked to one of my other mobile lines. If I don't pay this they cut the main line. How pathetic and how long do I have to pay for something that I don't want or use since 19 October 2021?