Here is an article mentioning the studies and other toll free number research

Quote:

Research shows that consumers who are looking though the phone book to find a business are much more likely to call one with a toll-free number than a business with a long-distance number. In a study conducted by telecommunications R&D company Telcordia Technologies, formerly Bellcore, paper ads were run that were nearly identical except that one had a toll-free number and the other didn’t. The ads with the toll-free number received six times the number of calls than the ads without the toll-free number.

Here's a brief, very brief article http://www.nytimes.com/allbusiness/A...gewanted=print