Ah, I feel for you. I had to do this as a volunteer and was so nervous, but you are right it will likely get easier with practice - that was my experience.

I really like the above suggestions, 'dial a smile' is one phrase that I used to keep in mind, and I would keep on thanking the person on the other end for their time and patience. They almost always responded positively and actually in the end I quite enjoyed the task. Good luck and let us know how it goes!