Cancelled contracts

I cancelled two of my cellphone contracts at the end of March 2017, paid the cancellation fees and sent all the documents as asked for by Vodacom. Since then they kept on sending me accounts every month for the same cancelled contracts. The documents were sent numerously to their retention department with no response. After I reversed the last debit order, my phone is ringing one stop asking me when a payment will be made to keep me talking. I just need my money back.