Can my employer creep text messages on my personal phone if:

Our building has next to no cellular reception inside. They offer us a guest wifi to log into.
I don't do anything illegal but I started using Proton out of paranoia.
We are a government contractor so I'm always afraid they might overstep their reach and try to look at text messages, etc on personal devices. Is this a thing? How can I make it more private? Or am I just overreacting.

Obviously if they had probable cause, this would …

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