Debt collection. But I've never had any credit in any form given to me by standard bank

I received payment demand from a company called nimble claiming to be standard bank . I've never received any kind of credit in any way from standard bank . No overdraft , no loan , no credit card , so I do not understand how I could owe standard bank 4200 rand. I had one normal account with standard bank that took me multiple visits to get closed many years ago but it was a normal account with no options of credit in any way . The only money used was that which I had in my account. *** who is nimble and how does standard bank create fictitious debtors and sell the **** debt to companies ?