Cancel expired contract

My 24 months contract with vodacom ended in the middle of June and I phoned them in time to say they must cancel it because I don't want to renew. They promise to cancel it but strangely enough I was receiving calls from their upgrade department trying to convince me to upgrade my account but I was refusing. On the 1st I realized that the Sim card was still active and they put monthly data and today I got the statement. I really do not need this account anymore and vodacom cannot force me to continue with while my contract is finished. Can you please help me to get out of this situation.

Regards Elizabeth Mdiniswa