Unsatisfied and angry

I got a call to tell me that I had taken out a loan of some kind with them. They even got my banking details, e-mail address and i.d. number. From where I don't know! Now I have to pay them R1900, which I never will pay because of the mere fact that they never send me any documentation to sign or a sms to say anything about this. I am truly dissapointed in them and will make sure that everybody knows that they just take it that you are the person applying for the loan without consulting you! I am currently without a job and can not eveb afford a loan at this time. Please advise on what my next step should be as I was handed over to a legal firm.