Could they? Yes, probably. So could the network providers (which would be more likely and easier). Would they? Ehhh, I feel more likely would be the government trying to mandate surveillance of communications rather than blocking them.
I don't think any company would want to be that overt about trying frankly. While the west is largely not primed for a revolution at this moment, in a hypothetical revoluton I don't think companies would make an overt position like that. It's not like companies would be dismantled overnight normally, they would want to keep existing.
Communism no iphone, so yes.
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