Why is it simple? Because you should never, ever need to use personal equipment or other resources for work use. If you're on-call, then the company should be

Why is it simple? Because you should never, ever need to use personal equipment or other resources for work use. If you're on-call, then the company should be providing the equipment needed to do those on-call duties, and pay for phone and internet charges accrued. If you're needing to use your personal stuff, then there's a problem, and the first thing to do would be to communicate this to your boss, and get the necessary equipment provisioned, be it a laptop to take back, or something else. Implicit reliance on your kit isn't even in the company's interest--what if it broke down, infected a customer with a virus or whatever. They and/or you might bear some liability for inability to provide service or to provide a bad service.