Vodacom debit my account- contract expired and cancelled in October -now in December 2020

I cancelled an expired contract with with Vodacom and they are still taking money from account. In September 2020 my contract ended, to my surprise, they were still taking money, upon enquiry I was told to phone if i want to cancel, which i did, it is now December 2020 and another debit just went through, and every month i phone and they promise to return my money, that is till not done.

I am very disappointed with their service, i will now have to block them at the Bank as this cannot keep happening. every time i phone, i am told it is cancelled and yet I lose money.