Incorrect demand to settle ABSA credit card

I need urgent intervention regarding credit card with reference number: ***. I was previously advised that I qualify for a settlement discount for this credit card which I accordingly paid. To my surprise, I am now contacted by a different collection firm (NBA/HP Attorneys) alleging that I still owe the settled debt which was accordingly settled with NDA. All supporting documents are available at my disposal. I fail to understand how ABSA has handed over a settled account to different lawyers. This should be urgently resolved.