I use my personal communnications devices to communicate with colleagues when communicating in a personal context.

I use my work communications devices to communicate with colleagues when communicating in a work context.

I suppose some people may have employers that prohibit them from having personal communication devices in their place of residence, but that's going to be a very different high-security type environment anyway.

I don't have a problem with asking a colleague to give me their personal cell number on a work communications channel. I don't think I'd want to work in a place where doing so was prohibited.