If you are a manager of any notable size of office or especially a doctor, you'll need someone answering the phone for you when you aren't there. Especially when you have a business to strike!
Personally hire the services of a professional answering service, rather than having to contact my voicemail constantly to check for emergencies or worried calls from patients.
Having a service answering the phone for me means that I can take trips or relax without worry and I don't have to reveal my personal information. If some emergency does come up, the answering service will put it through to tell me that I better call back immediately because, for example, Mrs. Jones is about to have her baby, or Mr. Smith has a recurrence of that stomach pain and may need to be hospitalized. It really takes the worry out of being a doctor to have someone answering the phone for you.
Of course, there are a variety of answering services to look for. If you work in a large hospital like I did until recently, there is an in house answering service of sorts. The desk will be answering the phone and telling me if there is anything that needs my attention. Unfortunately, they are pretty poor at judging the difference between an emergency and something routine that can wait for the next day while I'm out for dinner with my family.
They would really call about just about everything, ringing my pager for routine medical questions that I could have easily answered in the office the next day, or pestering me about people wanting to reschedule at all hours of the night.
It's important that the people you have answering the phone don't ere the other way, both for legal reasons and for the long term safety and health of all of your patients. I had a colleague who just such a thing happened to.
It seemed that his answering service couldn't be bothered to call him in the middle of the night, no matter what. After several nearly serious mishaps, including one with a patient who had a serious reaction to a medication prescribed by him, the doctor told them specifically, that if there is any doubt they should call him when answering the phone just in case there is really a very serious medical emergency.
Unfortunately, they were tragically negligent. Someone, complaining of stabbing pains in his stomach should have been hospitalized immediately, but his doctor wasn't told by the answering service, so couldn't do anything about it. The man almost died from acute appendicitis, which just goes to show you how important it is to demand the highest of service.