When you sign up for a free Google Voice account, Google gives you a free phone number. Incoming calls can simultaneously ring on up to six phones linked to your account. Outbound calls can be placed using the Google Voice Android or iOS app, or from Google Voice on the web.
You can schedule, screen, and transcribe calls with Google Voice.
- Schedule which of your phones rings when someone calls your Google Voice number: Ring the office line on weekdays, or ring your cellphone in the evening. (Gear > settings > edit button under selected phone line > show advanced settings > ring schedule)
- Screen incoming callers, so that calls from people in your Google Contacts or Google+ Circles get through while other callers must identify themselves. (Gear > settings > groups & circles > edit various call settings.)
- If you miss a call, Google Voice can attempt to transcribe the message. Depending on the caller and message, you may not have to listen to voicemail at all: you can simply read it. In my experience, transcriptions vary from hilariously wrong to highly accurate. (Gear > settings > voicemail & texts > voicemail transcripts.)