Paying LCS Financial - settling, verbal agreement

Hi all, I'm talking with LCS Financial about settling. They are offering me a pretty good deal for my debt owed, but I have to pay by Friday. It was done over the phone and I know it's not a scam, but I'm worried about whether I should try to get it in writing since it would suck to pay a lump sum and have it not be approved by the original creditor.

It seems loan companies rarely put things like that in writing before you pay, but it still seems shady. Has anyone settled with them before? Can I trust the verbal deal?