Vodacom still charging huge amounts on Debit order even though i have cancelled the contract and have been on Pre paid for over 2 months

I chose to terminate my contract(3 months ago) with vadacom after atleast 18 years with them. I did this seeing that they started to over charge me after 22month of current contract period . So I paid an" early" cancellation fee to get out of my contract. however today 01/11/2019 the still put through a debit order for a huge amount even though i have been on pre paid for 2 months... Problem no is that it is impossible to speak to a consultant over the phone as I am no longer on contract. So could you please assist in contacting Vodacom for this false ********** billing.

regards Michael