Vodacom keeps adding extra time and data to my contracts without my permission

I have 2 contracts with Vodacom. In February 2024 I had a 1 gig of data added to my contract ending 3649 and extra time on my other contract ending with 8731. The agent assured me that this will not be a reoccurring request. In March the extra data and time was added on. I called in the 27th March to cancel it and was told by the agent that it has been canceled. April month the data and time was added on again. I called on the 18th to cancel it and again on the 29th just to make sure that it got cancel. Today us the 1st May and the data and time has been added again to my contract. I am a pensioner and cannot afford this extras that Vodacom keeps adding to my contract without my permission. The time and data is going to waste and if I don't pay for it my contracts is suspended. I don't know what more to fo to get rid of this extras that Vodacom keeps forcing kn me.