Contract canceled, but Vodacom still debiting me!

I had a contract with Vodacom and because I did not like their service, I had my number *** ported to another service provider. Vodacom still debits me. All efforts to contact them have failed as they put me through a number of staff who cannot assist. Also tried emailing them but no response whatsoever! I am at my wit's end as I am a retiree and cannot put up with this! This is "*****ing" Vodacom, please cancel my debit order immediately and refund me what is due to me!