Cell C do not cancel debit orders

I cancelled my debit order with cell c as my contract had come to an end. A consultant phoned and confirmed that the last debit order would be in June and from the beginning of July the contract would convert to a pay-as-you-go. I still had many minutes available which cell c removed from my account (as agreed) and they converted me to a pay-as-you-go but continued to debit my account for the contract value? This is the second time I am querying, I have contacted Cell C 3 times via their website and still no feedback?