Discovery Bank harassment

I have never app**** for a loan or an overdraft with them. Also never had a Discovery Bank Credit Card. Yet I keep on receiving sms's from them that I owe them R4 879.67 and that I need to pay immediately to avoid them from handing me over to a debt collector. I receive these sms's on a weekly basis and it's been going for probably more than a year now. I phoned in and they lady could not explain how I can owe them money if I never had a loan or credit card from them. She were going to go into the matter to resolve the problem and get back to me. Up to now I have not heard anything from her and it still receiving these sms's. If I really owed them this money for more than a year, why have they not given me over to a debt collector as they have been threatening weekly to do for more than a year. I think they busy with something *******ly by sending these messages and most probably most people get a fright and just pay without really owing Discovery any money. As I do not owe them any money I am at the point of seeing an lawyer and laying a charge of harassment against them as that is all it is.