MTN contract ********* conduct

I called to cancel my contract and received an sms that my contract will be canceled on 13 June. I called again after being billed end of June I was told there was a system error and the the request of closing contract was left open so they closed out the action on 11 July before July billing cycle. MTN Still charged me for July even when they managed to close the contract before July billing cycle. I called MTN and I was told it was a mistake and they will revise the statement. It was all a lie a statement was not revised and now I have to pay because mtn did a mistake. Mtn contracts are nightmare to close they will reap you off, please be careful when getting into contract with MTN as it's likely you will struggle to close the contract they will bill you and blacklist you for their mistakes which they admitted too.