My employer provides a work phone and subscription, and I am free to use it privately. I've chosen to keep that phone work-only, so I have bought my own private phone+subscription, and never the twain shall meet.

The work phone gets left in a locker at work along with my work laptop, I refuse to bring it home with me until I have agreed in advance to work from home for some specific task. I know a lot of employers expect their employees to be available at odd hours, but I refuse to participate in that.

I made this decision after suffering under a boss who would call and email at 22:00 and expect results to be ready on his table next morning by 8:00.

Only a very select trusted few of my colleagues have my private phone number, and they will only ever use it in a dire emergency.