Encore Catering & Culinary Services interview questions

Went in for 3 interviews will all the management staff- basic conversation and qualifying questions. Process took about a week. During the last interview they talked to me about salary, we agreed upon a number and shook hands, the next day I came back to sign the papers and my offer was $4,000 less than we shook on the day before. When I asked why, the answer that was given to me was "we'll that was just talk." Very sketchy.