There are actually tons of different options. They can bully the ISP providers into shutting off services for a specific amount of time. They can shut down nuclear power plants that provide power, or make other utility companies shut off services. That automatically disconnects the majority of the population from the internet.
The truth is, we have no idea what kind of technology the world governments hold. We only know that they have an unlimited amount of money and people who can be blackmailed or easily corrupted into doing exactly what they want.
They could wipe out power but there are still thousands of self-sustaining remote sites still functional. I think we could agree on many scenarios that could possibly happen but most are unlikely. I'm thinking about method and how it is actually executed. Say, it was me executing the commands to disable software and/or hardware.