Kanto requires you to get the radio card...
Try doing all the other gyms first + rail pass + radio card.
I've got a quick q. about ss aqua. 9I can't remeber if it was same in crystal)
-Do I have to sail both ways to rematch people on the boat?
ie; I went from Olivine -> Vermillion, and the next week again Olivine -> Vermillion, but the second time no one wanted to battle me.
Would I have to do Olivine -> Vermillion -> Olivine -> Vermillion to get them to vs me again?
And a tip for those calling Gym leaders for remtaches, you can pretty much call them as many times as you want within their allocated slot:
ie; Sunday Morning call Erika, defeat her, go outside the dojo, call her again, beat her, etc etc. You can't call them from inside the dojo though (bad reception)