Freight Bill Post Audit Services

Has anyone ever used Post Audit services for their business? Im looking for some freight bill post audit services that I could use for my business?

A couple of questions Id like answered are:

How much does it cost for a freight post audit?

Assuming I want to begin a post audit, what steps do I need to take?

What do I do if I don’t have all of my company’s carrier contracts?

What type of recoveries can we expect if we begin a freight post audit?

Any replies would be appreciated.