I think the solution will be a separate device. Even if you tampered with the one you're given, you're still running on their network. Even if you wanted to just chat over Bluetooth mesh with your fellow Winston Smiths, this doesn't seem like a good idea.
In the border regions with China, some people who want to communicate with the real world, have phones that connect to the Chinese networks. A satellite able device would be better but probably too expensive.

I think it's that or we nuke ourselves into oblivion as a planet.