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Is it a valid debt that you do not dispute?
If so, I would take the PFD and a letter saying they will.
The problem with paying by 2 tomorrow is that you won't have a letter from them by then promising to delete it from your credit report. Never trust a collection agent. Get everything in writing, including the deletion, before you pay. When a collection agent demands payment before you can get a letter from them, it's often because they don't intend to honor their promise to delete it.
That is not necessarily true. Many, many times posters have had a CA honor their word that a TL would be deleted. Sometimes you just have to do it and hope for the best. An oral contract is just as binding.