Vodacom - Cancel Contract Conundrum.

I have been trying, unsuccessfully, since May to cancel my cell phone contract with Vodacom. The contract was to expire mid-August 2018. I followed all the various instructions to cancel the contract, from calling Customer Service to going into a Vodacom Authorized Dealer on several occasions. Never is there a reference number given confirming the instruction to cancel, never can one sign a cancellation contract/document. Despite being assured that the account on the Vodacom System is on Pre-Paid and therefore no longer on contract, I received an account for August and my bank account was debited. Upon making inquiries I was again re-assured that I was now on pre-paid and the August Debit Order was the last one. On Saturday 15th September I received my September Vodacom Bill for R4.99 for voice Roaming. I cannot roam on a pre-paid account. Not only has it been more than difficult to cancel the contract, I have been inundated with sales calls to upgrade, to renew and to sell new products to me. Not one of these poor consultants was informed that I was not intending to renew, they could not find the information on the system (or so they said) and I had no reference number to prove that I had cancelled the contract. Customers should be entitled to sign a form cancelling the Debit Order to Vodacom rather than be at their mercy to stop the debit order. Surely this is possible. We cannot be held "captive" by companies to whom we make out a debit order for a service. Why when the service contractually lapses does the debit order not automatically lapse. Perhaps the banks need to set up a debit order that is date linked to the contract. With Vodacom it is all to easy to sign up for a contract but seemingly impossible to cancel. Please Vodacom come up with a better customer-service based method of cancelling a contract. Customer service is not only about selling. The current process (if there is even a process) is not user friendly and leaves the customer feeling frustrated, helpless and eventually angry. Never again will I ever enter into a contract of any kind with Vodacom.