Toastmasters
I want to add that I also joined Toastmasters to deal with my general social anxiety. For some people, I bet curing the social anxiety will cure the phone anxiety too! It sure helped me!
How to overcome my aversion to phones
It made me
Happy 
"Finally understanding why I have an aversion has made it possible for me to work around it. What an improvement!"
How I did it:
I finally figured it out!
I never knew why I had an aversion to phones. I just realized one day that other people were much more willing to use the phone than I was. I asked for advice from coaches and therapists. I had my hearing checked. I even tried making phone calls to "build" my comfort with using the phone.
Finally, after years of wondering, I found the problem. For me, it's something called Auditory Processing Disorder. This paragraph from Wikipedia sums it up nicely:
"APD can manifest as problems determining the direction of sounds, difficulty perceiving differences between speech sounds and the sequencing of these sounds into meaningful words, confusing similar sounds such as "hat" with "bat", "there" with "where", etc. Fewer words may be perceived than were actually said, as there can be problems detecting the gaps between words, creating the sense that someone is speaking unfamiliar or nonsense words. Those suffering from APD may have problems relating what has been said with its meaning, despite obvious recognition that a word has been said, as well as repetition of the word. Background noise, such as the sound of a radio, television or a noisy bar can make it difficult to impossible to understand speech, depending on the severity of the auditory processing disorder. Using a telephone can be problematic for someone with auditory processing disorder, in comparison with someone with normal auditory processing, due to low quality audio, poor signal, intermittent sounds and the chopping of words. Many who have auditory processing disorder subconsciously develop visual coping strategies, such as lip reading, reading body language, and eye contact, to compensate for their auditory deficit, and these coping strategies are not available when using a telephone."
Lessons & tips: I recommend checking to see if you have Auditory Processing Disorder. It may be the problem!
Resources: http://en.wikipedia.org/wiki/Auditory_processing_disorder
