A general advice would be to try speaking a bit slower(I almost sound out each word sometimes)Yes it might feel a little awkward, but if it makes you feel better who cares right? Another thing which I personally have found helpful is to have a little post it note where I write down my introduction, as I have always found it easier to read out my post it note every time I make a call. I think it makes me feel more sure of what I have to say and makes the experience feel a little easier.