At a Tesla Supercharger out on the road in whatever state you are in you do not need your phone. You back into the Supercharger, once you plug in the Supercharger recognizes who the car is registered to and payment will be made via whatever credit card you have in file for payment.
The beauty of the Tesla is that you never turn it On or Off, just get in or get out and walk away. There is no key for a Tesla, approach the car and it recognizes your phone and thus your profile. It will adjust the seat, adjust the a/c or heat, tune to the music that you like etc. Now u can do all of this without a phone, Tesla gives you a plastic card the size of a credit card that will handle all of those functions that I just mentioned But you do need to have one of them with you. Tesla figures that most people have their phones with them 24/7 so they saw no need for a key. Personally I love it. It’s my wife’s car but when I drive it it recognizes my phone and everything in the car changes to suit me. That’s all I gotz!