I so feel your pain, I think some of my hosting customers are just lonely and need somebody to talk to.
I do use vonage and turned on their transcription service so they will transcribe the phone message in my voicemail and send it and the audio file to my email. It saves me a ton of irritation cause I detest voicemail and I can see if it's important or can wait without breaking from my computer.
It usually takes me a while to train a customer to work via email, I explain to them that it is the most efficient way to communicate on a project because all the information is stored and can be reviewed and people are less likely to forget something.
I'm not the best phone person, but I find a meeting schedule like a weekly call helps cause everyone knows there is a planned time for updates, and If I must phone, I'll take one call that is scheduled over 3 times a day for every random thought that goes through their head.
-=j=-