Ok, I finally figured out what happened here. And I'm thinking that PFD may be my only option - maybe I'm wrong though.
Over a year ago, I worked for Sprint. Sprint employees could add friends/employees to their accounts for a steeply discounted rate - only exception was that the employee was financially responsible for the account. This was one of those accounts. I started to have issues with this friend, and I kicked them off of my plan and onto a standard plan. At some point in time, the name and address were changed on the account- but that is another issue entirely.
Anyways, apparently there was a balance left on the account that I didn't know about. Sprint started trying to contact me (the employee and owner of the account) about it in November 2008. However, they tried contacting me at my sprint.com e-mail address. Which would have been fine, except I left Sprint in October 2008, so I never received any notifications of the past-due balance. According to the rep I spoke with, Sprint never tried to contact me except via e-mail.
Is there anything I can do at this point, or is PFD with the collections company my only option? Thanks again!