Paid up letter frustration.

Like everyone else on this platform, I am struggling to get my paid up letter from these people, instead, I get automated calls every week harassing me for payment on an account paid up in February. They are frustrating and ***********. Numerous calls (last one being yesterday 11.05.2021) has not only given me no result, but actually made their automated calls to go to overdrive. How do these people continue receiving work from companies with this level of incompetence?