"They are rooted in childhood—which is the only time stuttering can be reversed. Once you’re an adult, there are only ways of hiding" Don't think this is true. Bill Walton and Bill Withers both were in their 30s before they stopped stuttering I believe.
In the past I refused to use the phone. I couldn't. I would be vocally paralysed. Today I spent an hour talking on the phone to a mortgage broker.
The only situation I struggle with is conference calling at work. I haven't thought much on it as I rarely do it. I guess I worry I will get stuck and someone will talk over me.. which I guess is silly. If I did it more I am sure I would master it too.