I love talking on the telephone, I think it helps so much in regards to your stutter, one thing that is great and that you probably realise is that stutter is linked to breathing, right? So when you're on the phone you just need to slow your breathing down and when you know that you are going to stutter on a certain word, take a deep breath and speak in between that word and you will be able to say that word without stuttering, it's really.. weird. Try it and let me know if it works for you, it works for me.