Cancellation of Vodacom contract

My contract came to an end in November 2019 and I intended on cancelling the contract and switching to prepaid. You can not do it in store and must phone either 082 11 or 082135. Trying to speak to someone with these numbers is a mission in itself as the call keeps dropping even when I phoned in store. Once I got through they told me the contract has been cancelled but the following month I still received the contracted airtime etc meaning I’ll be charged again at the end of that month.

I have just received my statement and lo and behold i have been charged for another month. HOW CAN THIS BE LEGAL.

I have no clue what to do.