Unfair treatment by Absa bank to an unemployed person

I had a credit card and I lost my job due to retrenchment, I called Absa to inform them they sent me a form to fill. I sent back the form with the docs form work after some days they gave me a letter as proof that the credit card is paid. Now all of a sudden I’m been called to say I owe them money and this thing now it’s stressing me as I’m still not working I don’t know this insurance work I’ve been paying this credit card every month while I was working