What are you doing to get around gatekeepers? If you don't mind me asking. What industry are you in and what % of your calls do you connect to a Gatekeeper?
What about something along the lines of "Hi. Maybe you can help me out. Could you tell me who oversees your X (Marketing, Facilities, etc) department? I'd like to mail them a letter."
With luck, they'll give you a name, a job title, and that'll be plenty for you to call back with later and as casually as you can (as if you know the person you're trying to reach) say "Hello, I need to get in touch with Tony. Can I speak with him briefly?"
It's an art form, I know - as Vigilante says.. pays to do the research. The more you can act like an old college buddy, the better.