Vodacom ignores cancellation calls

I cancelled my data bundle on December 31st 2019. At the end of February, they deducted the full amount of the contract from my account. I phoned them again. After being on the line with them, talking to two different people they told me that my contract was not stopped in December but they stopped it know and will fix my account with them. Today I received an invoice again from them stating that they will deduct the amount from my account again end of this month. This is absolutely rediculous. How many times do I need to phone and cancel the contarct.