Failure to cancel contract

This service provider is an absolute nightmare to deal with. To start with the events that lead to me canceling the contract, at the end of 2017 I switched banks and after 3 failed attempts to change my debit orders to my new account I just gave up. Now every failed debit order also resulted in penalties that I was liable for. So early march I went into the Menlyn Branch(the one near New World entrance) with cash in hand, laid my case and requested the amount I owe them to fulfill my end of the contract they gave me the amount I paid it and requested my contract to be terminated with mediate effect, the payment was captured documents was prepared I signed them and upon completion I asked the consultant to confirm that I'm done now with Vodacom and would never have to deal with them again and it was confirmed by the consultant. Then somewhere around July/August Last year about 2 months after my contract was supposed to end email in my inbox again a Invoice again I ow Vodacom for the two months past and the month ahead(for a contract I payed up about 5 months ago and terminated) this lead to allot of time and airtime wasted calling into call centers to resolved the issue and multiple trips to the same Vodacom shop where the "manager" eventually assured me he would deal with it.

And all went well haven't heard from vodacom since whom has got all my contact details untill now when I got " RE: NOTICE OF INTENTION TO COLLECT ARREARS DUE TO - Vodacom (pty) Ltd " in my inbox from VVM debt collectors.

I'm fed up and don't know what to do other then sharing my experience publicly, and I've got no confidence what so ever that this will get resolved but after all the money and time wasted and the frustrations caused by Vodacom I'm not giving them a cent.