Billed but never used SIM card and cancelled contract months ago!

I settled my vodacom contract at the beginning of the year and had no further charges or invoices for a few months - then all of a sudden for June 2018 i got billed R160 out of nowhere...so i called Vodacom and they said it was for usage on my contract sim car which was nonsense because i paid it off long ago and never even put the sim card in my phone. Then i called again and the lady did an immediate cancellation for me, but yet again i got billed for July for just over R200...i thought that the cancellation was done??? The lady said that they will do an audit and refund me when the process is concluded...but then i still got billed again for never even using my sim card??? I want my money back and won't take out a contract with Vodacom again!