I keep saying this but you do not have to “cold call” or telesell directly into the office of senior level people. It can be very hard work trying to catch them between meetings and then when you finally get through it can be a challenge to get them engaged. So do the work through the PA, let her set up the 15-20min introductory call, make sure you have a good agenda which gives structure to the call and you know when you call they are ready and prepared to take your call!
I have just done this for one of my clients making an introduction into one of the top managment consultancies. They are delighted!