Settlement Letter, unknown additional fees

So since March I've been waiting for a settlement letter from ADRS to date. To my surprise i receive a sms notifying me that they've escalated my matter to external debt collectors because there was a figure that miraculously appeared after i settled my account. All agents can't give me an answer about what the fee is for and dropping calls in my ear instead of trying to assist me with this matter. I'm disappointed in the business and way of how they handle situations.