I see I can add the Hotspot feature online. Does Sprint allow you to add/remove it monthly? I don't need it all the time, but some months I do travel a bit (and I want it more for the multiple device support rather than just tethering to a PC) but some months I would not use it at all. I assume I would pay for it for an entire month and then I could cancel it for the next month - but can I do this as needed easily?