After leaving four or five messages without receiving a response, you should stop calling – at least for now. Don't expect the courtesy of a call back from a hiring authority. Unless they have a need for someone like you, it is not likely that they will call you back. Don't take it personally. If you are looking for a job or soon may be, join Tony Beshara for a FREE webinar: The Top 10 Reasons You Might Have Trouble Finding a Job (and How To Combat Them).
Not only do you sound more articulate and confident when you're not rushing to the finish line, but you also sound more authentic. Speaking in a rush suggests you've been dialing all day and need to be as efficient as possible. Yet if you're making three calls rather than 30, you're probably going to sound far more deliberate. A slow finish tells the buyer they're not just another name on a list.

Take a deep breath before beginning and stay calm while speaking. Try practicing a few times beforehand if you need to. No rule says you have to build out what you want to say on the fly.
“Hello ____. This is _____ again, calling from ______. I ran across some information on a client who made dozens of offers on houses before someone finally accepted one of them. We learned a lot from the experienced and I successfully used the findings to help other homebuyers make bids that were accepted early in the house hunting process. I thought I would share it with you in hopes of saving you time and making it easier for you to purchase the home of your dreams. I’ll email you the information. Give me a call if you would like to review it together. Thank you.”