I can't comment on RMCN Credit Services specifically. But no company can "fix" your credit in 30-90 days. It won't happen.
Take that $2,000 and pay off any outstanding/late debts. Talk to your credit card companies directly. Try to negotiate a lower lump-sum payoff from your creditors. Buy a book or two (tons of them on Amazon) on how to repair your credit.
But you might as well flush that $2,000 down your toilet as expect that you can get your credit fixed in 30-90 days.
Hope that helps.