My verizon account didn't go to collections agency, instead, verizon themselves reported on my credit reports as a charge off, for being just days late like you said.
Try PFD with verizon. Get a real copy of your report and see exactly what is on there, and who you need to pay. Verizon never sent me any thing in the mail stating I needed to pay, they just put it on my credit report.
On your real copy, there will be an address for verizon "recovery" department, this is who you send the PFD to.
I would advise against paying until you get the PFD in writing from them, because then you lose all leverage. I would also try calling the number listed on your real report to see if you can get them to take it off over the phone and fax you something in writing and pay then.
I hate verizon. Too bad I paid mine before finding this site, because I lost all leverage and am not trying to find creative ways to get this off my reports.