AFNI Old Nextel bill

[debtfree09]

My son had an old Nextell bill from 2004-2005 when he was in college.  He thought he had done that pay half and its paid in full deal. It was on his credit report and then it fell off (he has great credit now)  Low and behold about a week ago he gets a settlement offer from AFNI.  What should he do?  It's been so long since I had to deal with any of this, I've forgotten the steps.  Thanks in advance. 

[Shogun]

I'd start with a simple DV.  It's a really old debt, and obviously past the CRTP so it has been excluded from his CRAs.