debited for what i don't know

I got an SMS notification on my phone today when i checked it say debit order from Mzansi i don't even know the company i checked details on the internet got the telephone number and spoke to Camy Sintsh i asked her why is the amount of R99.99 been debited on my account she couldin't tell me she said i must give her a reference number and i gave her, all i want to is my money back and they must explain to me where did they get my banking details from as i never gave it to them, who gave them the authority to debit into my bank account, i far as i am aware this is ***** they are not suppose to do that . I want my money back they must never ever do that it is called *****ing from somebody you don't even know