MTN wont allow me to cancel contract

I have a contract that is ending on the 10th of July 2019. I contacted MTN on twitter last month to ask them to cancel the contract on the end date. I do not have this sim anymore and dont need it. They told me to contact their call centre on the day after it lapsed but I need to give 30days notice. I explained that I do not have an MTN number to contact them so that wont be possible. ALSO they want me to pay another month after the 10th of JULY as I am not allowed to cancel before hand, so I cant give 30days notice before the 10th which is ridiculous. They said they will contact me I still have had no luck. I will not pay another installment for this contract as I have proof that I tried to cancel. I WANT THIS CANCELED AS OF END OF 2YR CONTRACT WHICH IS THE 10TH