Poor Service MTN/Mondo

I took out a contract with Mondo. When the cellphone was received, the item delivered and what was offered online did not match. I took the phone within the specified time frame to MTN to return the phone and cancel the contact. I received confirmation that the contract was cancelled, however MTN tried to deduct installment from my bank account and when that failed, they tried to recover the money of the phone which I no longer had. They also sent me an SMS to say I was reported to the credit bureau. This is unacceptable as I have done everything on my end to cancel the contract and returned the phone within the stipulated time frame. Got another SMS this morning saying they are going to deduct the full amount of the cellphone from my bank account again. Each time there is a cost on my end to reverse the debit order. Not impressed with MTN/Mondo.