MTN South Africa being ***** robbing its clients

My husband’s 24month’s cellphone contract was ending in April, he went to the store to cancel and was referred to do it via the phone. He phoned several times and was reassured that it is cancelled and it’s now on Prepaid. End of month he received an invoice of a high premium, he’s been attempting to call with no luck until tonight we have been informed that instead of cancelling the MTN assistants has been upgrading. What *****ster is that huh?