I had a contract of 10gig of data per month for 24mnths and it expired at the end of May 2021

I had a contract of 10gig of data per month for 24mnths and it expired at the end of May 2021. Firstly I could not use it as the there was no coverage mot of the time, but I paid until May 2021, but now they are still debiting my account, I don't know why coz I even threw away that useless Sim card of theirs, and I know they don't load data if you are owing. So what do they want me to pay for???? Their contact center is not picking up, even when I call the branch at Mall of the South, where I bought the contract. there is no response, I can't even log my query online, I always reach a dead end.