At least with my OB/gyn's office and my primary Dr's too you call and get a recording. One of the choices you can pick is to speak to a nurse if you have clinical symptoms. Other than that you talk to whoever answers the phone and they take a message and then call you back with an answer. Even when I call with a message or question for my pdoc someone who answers the phone emails pdoc my concern and then pdoc may or may not call back- it depends on how busy she is. It also depends on how serious the nature of my call is. Same goes for my OB/GYN' and my primary doctor's offices .

How serious is the nature of your call? My pdoc's office has a service that you can call when the office is closed. They can tell you if it sounds like you should call 911.