Poor service

I bought Alcatel tablet with Vodacom and I was offered airtime contract and I signed up 2 years (2022) back in April. This year 2024 around February , I received a call from a gentleman advising that the contract is coming to an end and they wanted to know if I wanted to continue or cancel? And I said please cancel it because the tablet is no longer working. In March 2024 I received another from a lady and I advised her please cancel it. Can believe they were billing until I check my statement last of August and I realised they were billing me, mind you they've been billing me for 5 months without me knowing. I called requesting cancellation and refund back to my mrp money card. Shem they did cancel credit me with 3 months payment because the other 2 month they're not sure if I used the airtime or not which it doesn't make sense to me but I was like it's okay as long as it's cancelled. I went through this month billing and guess what, I am charged again. When I called the lady I spoke to told me it was cancelled but really now what does one has to do for the billing to be stopped and reversed?