Constant phone interruptions can break up even the most dedicated workflow. However, you can solve this by setting aside a specific time each day to return and make your calls. Productivity blogger John Cox has more:
Folks will leave you messages. Return those messages at a set time. Try to say between 10AM and 11AM in the morning and 2PM and 3PM in the afternoon is the time that I call people back. Not before, not after. I suppose there could always be exceptions to the rule due to emergencies, but to be honest with you, I haven't had to make the exception. The only reason that folks expect an immediate return call is because we train them into that behavior.
I've had to do this since I started working exclusively from home, and it's cut my distractions down pretty drastically. If you've set aside a specific phone time, please share in the comments how this is working (or not working) for you.