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.