Wrong Business

My contract with Vodacom expired in September 2018 and i notified them on the 25 August 2018 that i will not renew at a Vodashop in Southgate Mall. I received an sms with ref number: 1- ********** ********** that my query has been closed. To my surprise my account was still debited in October 2018 when i followed up with them they said they sent me the airtime and there's nothing they can do. I've never used their airtime and they can take it back because i no longer even use their sim card since cancelling the contract. On top of it they also told me that they are still going to continue to debit my account in November because they already issued an invoice. This is ******** i no longer have an agreement with Vodacom and its wrong of them to still continue taking my money without my consent. Please assist me.