I did not want to carry around a pager and a cell phone so what I do is forward the office phones to my cell phone. Since I am solo, I tend to take my own call, but for the times when someone else is covering, I then have the message tell people where to call.
My message in general tells them to leave a voice message if they NEED to speak with the "provider on call". Most of the time people leave messages for appointments, occasionally they need a call back.
Now..the only thing I don't like has nothing really to do with this system...but I hate calling people when I cannot have my return number blocked (when calling from home or the cell number).
I've been doing this for over a year now...and it works. I found the key is what the outgoing message says (ie, call the pharmacy, when we are open, etc).
