Stop calling us.
Seriously. We do not want your phone calls. We do not want the phone calls where you call to "confirm the address of the agency" (as if it's written WRONG somewhere) and then begin to pitch your book while we're on the line. We're on to you. We know your tricks. The phone line is for business purposes. It's gotten to the point where many agents don't pick up their phones, including my boss, unless they recognize the name/number - which is bad, because my boss doesn't have caller ID and can never remember my number, so I can't even call in sick because she won't pick up the phone. I have to email her.
There are established ways to reach us: by post or occasionally by email. Please use those methods. I think I speak for almost every agent when I say this.