Like you, I hate being interrupted, especially when it has taken me about 20 minutes to assemble all the various threads of things in my mind so I can see how things inter-relate. If I get interupted then I have to do that again. My solution was fairly brutal. No telephone, only an internet line, which is a lot cheaper anyway.
So it was email. If there were things that could only really be handled by speech, then it was Skype by RV. If you want me to do something for you then its when it suits me, not the other way round. Of course, when you work freelance, then you have that luxury