I just have my phone permanently on silent / no-vibrate. And I check it when I feel like it (e.g. when checking HN or other news, between meetings, etc.). And I redirect unanswered calls to google voice to get the transcription of voicemail as a text.

If you’re not required to be on call for reason or the other, I can only recommend this approach. No wasted time with robo calls and also puts some humility into your hot shot boss that thinks it’s ok to try to call you about whatever at 1045pm. ;)