If you're away from work and you don't want to be called, switch your phone off. I have two phones, one is the work phone and one is my personal phone. My personal phone is always on in case my wife/family needs to get hold of me. If I get a call on that phone from a number that I don't recognise, or from a work number, then I'll happily let it go to voicemail. If I've left the office and I'm able to do some work, then I don't mind leaving the work phone on, otherwise it gets switched off.

It might not work for everyone, but it means that I can seperate work from home life.