SSDA won't stop harassing me!!!

They won't stop harassing me! I owed Discovery an amount years ago. I made monthly payments as agreed with SSDA. Discovery refunded me almost the whole amount and sent me proof that I owed them zero in 2021. I forwarded this SSDA numerous times years ago. Now they won't stop plaguing me with emails. Apparently I owe them years' interest on an amount that was clearly paid up in 2021! It is the most frustrating situation! I provide the proof and a week or two later a new consultant is striking up a new argument!