Shaw academy ****

I won 4 weeks free course with shaw academy in Vodacom,i decided to give it a try so i registered with shaw academy. When it was time to attend classes i realised that they sell study materials so i decided not to go ahead with it anymore. After two weeks i cancelled the account. Today when opening my banking app i found that they took R399 from my account without my concerned. I contacted them by e-mail and the refuse to return it saying i didn't cancell the account before due date which is a lie.I registered for free course,why should i pay if the course is really free?i need help please,i really need my money back