How did the CA get the credit card details?

My friend had a surgery in a hospital recently. The total bill was $29,546. Her insurer covered 90 percent of the expenses. My friend did try to negotiate with the hospital, but they didn’t agree to forgive the remaining amount. In fact, the bill has been assigned to a collection agency in Carpinteria. The collection agency called my friend and asked her to pay the amount through her XXXX credit card. They told that she has XXX credit limit on the credit card. How did the CA get the credit card details? She has paid $500 till date to the collection agency.