Unathorised debit

Hello peter there's a company named golden rewards that proceeded to debit R299 twice on the 1st of October that I didn't authorise. They called me early in September and told me their offer and that they have my details and I said I'm not interested yet they continued to just debit my account. How allowed is this since I don't even know who these people and they took my money for something I know nothing about. Give me back my money Golden rewards