Question. I have an iPhone 5s on Verizon, which I know is an unlocked phone and the same exact phone that Sprint and AT&T also use. Next summer, I am going to a NASCAR race located in the middle of nowhere (Eldora). I went last year and had no service on Verizon. Of course, since Sprint is a NASCAR sponsor, they bring a bunch of portable towers to the track and their service is the only service that actually works. Would it be possible for me to get a Sprint sim card and pay a month of service (pre-paid if possible) in order for me to actually have service at the track? I seem to remember reading that Sprint make it impossible for devices not issued by them to be used on their service. Anyone have an answer? Thanks.