There are pluses and minuses to every workplace. Mine is no exception. I'm not
going to waste space on this board whining about my employer, because I'm generally happy there. But a few years ago, there was one big peeve I had. Back then, I was on the graveyard shift. I would be trying to sleep, and the MIS Director would frequently call me, and wake me up from my sound sleep. Usually it wasn't to call me in, but to ask me a question which could have waited until the morning while I was still on shift. Well, I would pick three days a week to turn off the ringer to my phone, or just not answer it, so I could sleep.
So I offer this suggestion for you and your significant other: devise a "phone ring code" on your planned day off together. Tell him that you will let the phone ring twice, then you will hang up, and promptly ring again. That way, if there is no big delay after the second ring, he'll know it's possible his manager is calling him in, so he can ignore the phone. After all, how does his boss know he just hasn't gone to the store, or to visit a friend? At least here in the states, if you aren't on call 24 hours a day and have to carry a pager (I've never been on call), you are your own man on your time.
Perhaps the manager will get his shit together, and draft up a proper schedule.
None.