Vodacom ignoring repeated instructions

I emigrated in Feb 2020 and my existing Vodacom contact ended in December 2020. From Oct 2020 I started informing Vodacom via e-mail that the contract should be ended and not rolled over month to month. On the occasions that they did respond to me, I provided the information requested. The response was so intermittent and unsatisfactory that I also asked my bank to cancel my debit order as I didn't trust Vodacom to honour my repeatedly expressed wishes. Despite all my efforts, Vodacom is now sending me statements reflecting the monthly fee owed. I'm at a loss as to how to escape from this relationship.