We are two physicians (GI and Rheumatology) practice (husband and wife). At the end of the day, we forward calls to my cell phone with greeting message advising patients to leave a message for return call or call 911 in case of emergency. Once message is left on my phone, I review it and then decide to either call back or have my office (two staff members) to return the call on the next business day. Fairly do-able system and does not cost anything (have plenty of minutes on my office cell phone).
