You need to find out who owns the debt now. Does the apartment / management company still own the debt and are simply using a collection agent to help collect? Or did the apartment sell the debt to a collection company and they now own and service the debt?
If the apartment still owns it, then you may be able to reach a deal with them and have them recall the collection once paid. However, your son needs to be humble and admit his mistake in not leaving a follow-up address or contacting the apartment after he moved. This was caused by negligance, not an accident. If he is lucky, and goes in with the right attitude, they may remove the item from his report based on good will.
If a collection agency owns the debt, he will have to work with them directly. Lots of collection agencies will remove the item from his reports by paying, but others will not. He will just have to reach out and find out details and if they will remove if paid.
As far as getting something in writing and acting on it, you do have some recourse via disputes, CBFP, and perhaps the attorney general of your state if they don't follow through. You will just have to take it one step at a time to get it resolved. But even if they do agree to remove it in writing, you should wait 30-60 days before taking any action because it can take time to filter through the system.
If whomever refuse to remove the item, it is probably still best to pay it off and have it reported as $0 balance and let the healing process begin. The collection will lose strength over time, and if it is showing as paid, it probably would help him when he is ready to build.
At the end of the day, I wish your son the best. This was a mistake I hope he learns and grows from. But at the same time, we all have made mistakes, so he is not alone.
