Cancellation of unreliable LTE data service

We entered into a uncapped LTE contact with Vodacom In November 2022. Included was an Alcatel router. We had numerous problems with the wifi with signal often lost and very bad downloads. We contacted Vodacom support which informed us that technical support will contact us.This never happened, At the end of December we handed the Router back to Vodacom as we had no service. We requested a refund and cancellation of the contract. notwithstanding following this up on a regular basis it is still not cancelled and Vodacom continues to debit us monthly although we have no service and returned the router to them. This is tantamount to theft in my opinion as they keep taking money. It is impossible to find a responsible person whom you can deal with. As a matter of interest we obtained a LTE service from Telkom with which we have had no problem and we are experiencing a reliable data service.