They don't do anything, but want to collect fees when debt collectors reduce amounts to settle.
I had around $75,000 in debt from credit cards when I started with Mario(he left and told me I should too). I got a settlement, put $30,000 into my debt, and was told it should take care of most of it.
The "negotiator" never got me any good settlements with that money and instead of paying off my debt in around a year, 2 years later they want me to keep paying their fees. I also have to pay the "negotiator" fees for accepting the offers debt collectors send me.
I got sued 3x but debt collectors because no one negotiated a settlement before the court like they said they would. But they did get their fees for negotiating after the case was going to court.