Very unhappy client

I've cancelled my contract a few months ago and still after so many emails and also tried contacting Mtn holding on forever and no answering . They put you through to legal department and after 30 min still no answering. This is 2021 and the call centre say you cant leave a message for them only way to hold on. But with no answer. So how do you resolve this matter ?? And every month they still deducting .