I screen my calls on my cell phone and don't answer when riding. I'll stop to check who called and listen to a voice mail in case it is an emergency, but in no way do I feel obligated to answer ANY phone at any time unless I know someone is trying to reach me for immediate reasons (doctor, family health, meeting me somewhere, etc.).
I've also been known to fake a dropped call with someone who I can't get stopped (i.e., my mother).
My home is my refuge and taking a phone along with me outside is for convenience and safety, not to extend obligation, guilt and duress.
Caller ID and durn hardheaded-ness is a wunnerful thing. Get yours today.
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.