Two things worked for me. You will have to figure it out based on the person you are speaking to. The first one was playing hardball. The rep told me that if I paid the bill, I could get it deleted. So I said that I needed that in writing, which he said that they did not have a form letter for that, so they couldn't send it. I asked to speak to the supervisor. I explained to him that I had a very big line of creditors to pay off and that if I paid them with no delete, it was of no benefit to me, so I would be putting his bill at the bottom of the pile. I told him that the damage was already done to me, and if he wanted my money he would need to comprmise by deleting the TL in exchange for PIF. This kind of worked, but what really ended up working was that I told him that his rep very clearly told me that I could get a deletion, and he immediately approved it. I PIF and the TL was deleted immediately. Apparently, the fact that the rep mis-spoke was the key. He never verified it with the rep. Because the rep was probably talking from a script, getting him off the script and him saying that I could have a delete worked, whether or not he meant a TL delete vs. an amount owed delete...we'll never know. The CA double talk all the time, why not use it to your advantage. Ask the rep if the amount will be deleted, he'll say yes, and then tell his supervisor that he agreed to a delete, and you'll get it. They fear breaking any FCRA rules, so put the ball in your court.
The other creditor that I dealt with was IMC. I got someone sympathetic. I told him that I had gone through a divorce, I am now a single parent, and that I am trying to clean up the fallout from that and buy a house for my son and I, and that paying a collection without deletion won't help me at all. He pulled up my file and said that there had to be a valid reason for deletion. He then asked me if I had received a bill from them. I hesitated, trying to remember, and he said that the correct answer to that question would be "No". I said "No" and he was able to mark the account for TL deletion with PIF. Unless the creditor sent something to you certified or any other way that they have proof that you received it, then you can say that you never received the bill, that you are calling them based on the listing on your CB. Just be sure that when you call, you "have no idea what this collection account is for" when you inquire about it, that you are just trying to clean up your credit report and paying some things off. Just be prepared to pay by CC during that phone call, because the offer to delete may only be good for a minute!
Good Luck!