Worst debt collectors ever!! Disgusting behaviour and terrible customer service. Why is this company still functioning?

My Identity account was handed over to SEA sometime last year. I paid the full amount I owed last year in August. I've been asking for a paid up letter for more than a year but with no help. Promises to always send it but nothing for more than a year!! I tried calling them again today only for them to tell me that they no longer work with Identity so I must go sort out my problem elsewhere because they don't deal with Identity anymore. Imagine that. I've asked more than 15times for the letter! Today I'm told its not their responsibility like ***? This pain me so much because I can't get a home for my children because of 1 simple matter? ARA IS CRUEL AND INHUMANE