I'm surprised this hasn't been mentioned. But this is where VoIP/PBX is very useful.

You can have all your external calls show up with the office number and you can even take a VoIP phone home if you need to take calls from home. Most of the cloud VoIP providers even provide an app with their service that lets you do this for free from your cell phone. Downside is, usually you need WiFi for good quality.

When I call, I can use my office number even when I'm on the go.