Anxious About Making Phone Calls

Now I thought my anxiety about phoning people was just a dislike, my dad doesn't like it either and will avoid it and I do the same. Once I am on the phone or if someone initiates the call I will happily put on my posh phone voice and get on really well. I do fiddle with things and pace around once on the phone but it's not uncomfortable. But I hate dialing the numbers in and wait to hear hello. I often tell myself it's going to be fine your good on the phone. I type in the numbers and my heart starts to race, on good days I will put it to my ear, on bad days I will put the phone down and try later. I am anxious about how I will start the conversation especially if I need to explain something, the worst thing that will happen is I won't make any sense and won't get the right answers so I dont know why it scares me so much. 

I plan to ask my Therapist this week about it and will hopefully learn some techniques on how to deal with it.