Nothing says, "You’re not that important" louder than taking a call from someone else during a conversation. "But I have to answer when a client calls, I have a closing, my boss has a question, etc., etc., etc." No. You don’t
You do, however, need to set an appropriate expectation.
Decide what a reasonable timeframe is to return calls, text messages, and emails based on your industry and client base. Be sure to communicate this as part of initial conversation with new clients. It might sound something like this- "If you need to reach me quickly, please text. I can check those more frequently. I’m sure you appreciate how important it is to give each client my undivided attention so it’s usually hard to catch me by phone." They’ll appreciate it when they are the ones not being interrupted.
If there are certain calls that can’t wait, like your wife is going into labor any day, or your kid’s school, set a ring tone for that contact. Remember to set a unique vibration pattern for when your phone is on silent as well. Be careful not to let the definition of critical get too loose. If you do, you’ll end up right where you started answering the phone every time it rings.
When I have gotten a call like that it sounded something like this- To my client: "I’m sorry, it’s my daughter’s school. " Answer phone so client hears: "Hello, this is Michelle. Is everything alright?" After the call: "I’m so sorry for the interruption. I appreciate your patience."
If you don’t believe that any or even most of your calls can’t wait 30 minutes, I challenge you to go through your call log for the day. Look at each of the calls you answered and ask yourself, "Would 30 minutes have made a difference?"