MTN Contract can't be trusted

My mom has a contract with MTN ever since she take a phone contract there is always one problem after another

She was given the wrong package that that differ from the contract she signed

Later on she was told that her account was in errors thats when she found out that she was given a wrong package

We then agreed to pay the upstanding amount that was due and started the bill afresh

Since January we have been paying the bill with no problem and never skip any payments only to being told that we are in errors again

We have been calling non stop and the problem is every phone call you gine a different consultant and they all requested a proof of payment which she did send but with no help or even a reply

We are tired of calling them every day with no response from them and now as i speak thry close the line and they refuse to open it