MTN's customer service is abysmal

We have found it extremely hard to work with MTN. They forgot to debit my wife's account for her contract. Then she phoned and ask them just to debit it, at which point they only debited 90% of the outstanding amount, and thus her phone is still in suspension. We gave up and decided to cancel the account and replace with something else. We let them know, and they then added ANOTHER month's charge on the account. At which point the fight began to get it cancelled. The cancellation department (which we could only reach by dialing the ***** line then asking to be transferred, as the auto machine is just chaos) cant help us before we clear the account, which includes amounts not due them. The department they send us to to sort this out then end the call with us after a few minutes, meaning we have to take another 20 minutes going through the system to get back to them. We tried thrice. At which point we tried the whatsapp chat (which doesn't understand any version of "please let me speak to an agent") and Emails, upon which I got the explanation on how to cancel an entirely different account.

I know these companies make heaps of money by ignoring us when we try to cancel, but this is literally impossible.

If anyone has advice on how I force an interaction that will help us close this out, that would be great