I have to call my clients and my clients' parents on the phone at the beginning of each semester and sometimes throughout the semester ("Is it okay if I give your child M&M's as part of a therapy activity?" "Would you mind preparing a story to share with group this week?"). It's one of the few parts I don't like about being a clinician. I'm okay leaving a message because I usually write up a script beforehand, but if someone picks up, I really struggle with what to say--especially how to end the conversation. It's always this awkward "Have a nice day," "bye" "bye", mess of interrupting and stammering. Ick.
Oddly, I have very little difficulty informally interacting with my clients and their parents now. Thankfully I was placed in group sessions (first accent reduction with adults, then "phonology and language with literacy" for preschoolers) for my first two clinicals, so I could let the other clinicians talk to the clients and their parents during the transitions to the therapy rooms and out (and also use their conversations as a model). The clients/parents seemed to just think I was a quiet person. Now it's easier to take my individual clients from the waiting room to the therapy room and back and make "small-talk" conversation with them.
I still get nervous when I have to go over goals and semester reports, though. (Wow, sorry, I got quite a bit off the topic of communicating with phones).