Pick n Pay

To whom it may concern, I have a credit card with(RCS) pick n pay. When I went to the bank today to update my details, I found out that I apparently have another card that's linked to my bank account but it is not in my name, and now I have a bad credit score, I went to enquire about the matter at pick n pay hyper at Maponya Mall where I opened my account and the response I got was something else, they told me that they can not help me with the matter and that there's nothing they can do. So I don't know what else to do I'm in debt because of this other person who is supposedly a man and I'm a female If anyone knows how I can sort this matter please assist me