Bad credit card handlers. *********** staff

Tell me why I close my credit card account (Sept 2024), with a clear instruction to their employee after I have received my paid up letter . And then 2 years later Feb 2026 it comes up as Arrears with 4K that I apparently owe them . Only getting picked up when I am in the Bond Application Process . This is messing up my credit score. Haven't had any credit in the last 2 years & now this. Nonsense