DMC are the epitome of rudeness

DMC has embarassed me at work over an account which I settled almost 2 years ago elsewhere. Whenever I ask them not to call at my workplace, they are rude and impatient with me. I sent a query on the DMC site however this query has not been attended to. I am sick and tired of the calls and harrassment given that I have worked in the debt collections industry I am fully aware that when a debtor says DO NOT CALL on a certain number, this needs to be respected. At DMC they don't respect these wishes so they continue to call and being rude. Just this morning I was told to drop the call since I don't listen. How do I listen to a person who's treating me like I am not mentally stable. The RCS account was settled January 2024, I have queried this issue with RCS directly therefore I DO NOT WANT ANY CALLS OR CORRESPONDENCE FROM DMC.