When you reach a reporter on the phone, turn on your energy. Smile. You’re selling something, remember? Act like it. Don’t be a downer.
Also, take the gum out of your mouth, don’t make a PR call from a mobile phone, get to the point, etc. Reporters’ ears are highly attuned to tone and effort. When you’re phoning it in, we tune it out.
Rafe
Pro PR Tips 
I thought you generally advised against calling?
In a former life I was a journalist before people used email outside of the walls of their businesses. All pitches came in by phone or fancy media kit. I would bet journalists received far fewer pitches in those days.
I do advise against calling, except in emergencies. But if you do call, and the writer does pick up, being pleasant is the way not to blow it.