Any communication is best done via mail for record keeping purposes. If you discuss the account on the phone, there's no proof as to what was said or agreed to. If you haven't admitted you own the debt, then I suggest first sending a DV letter. If they aren't able to provide you with the required documentation, then the debt should be removed. If you have admitted you own the debt, then I'd suggest going ahead and sending the PFD letter. It never hurts to ask. You may have a better chance to get them to agree to remove it if you pay a good portion, or all, of what is owed. Maybe try sending the PFD letter with a low-ball offer. If they decline, send another and offer a higher amount that you would pay. If it's on your CR already, what's another 30-45 days of waiting, especially if it ends up going in your favor. That being said, if the file is set to fall off your CR soon, you might just want to leave it alone.
Whenever I send anything to a CA or OC about problems on my CR, I always mail everything with return receipt to prove I mailed it, that they received it, and on what date they received it on. So whether you go with a DV or a PFD, I'd recommend mailing the letter certified or with return receipt. You should also hang onto any documentation that shows the address that you were told to mail it to, just in case the CA argues they didn't receive it because it was mailed to the wrong address.
