Deducting fees for a cancelled contract

I cancelled a contract with Vodacom November 2021 and to my surprise I realised that they are still deducting a monthly fee even though it states on their system that the contract has been cancelled. Spoke to a very helpful lady in one of the departments but she could not assist me and referred me to the cancelations department. I now have to spent time on the phone trying to resolve an issue that was caused by Vodacom. How can you still deduct money on a cancelled contract. In my opinion that is *****ing from the consumer! Not happy at all!