Getting over my fear of talking on the phone?

Getting over my fear of talking on the phone? Hi, i've been looking for a job for a few months now. Sometimes I miss a call from somebody asking to setup an interview but i'm just so nervous on calling them back so i just never do. My stutter has controlled my life in that way for as long as I can remember. When I was little, I would have somebody call my cousin and ask for him then they'd give me the phone and i'd talk to him because I was afraid i would stutter while talking to his parents while trying to ask for him. Now that i'm older it's still the same but I can't just have somebody making calls for me all the time. I feel like i've missed out on great opportunities because of this and I feel so hopeless. I need any advice that you could give me.