Ill be headed overseas next week, for Paris and the U.K. I just purchased a new 6sPlus with the apple upgrade program, so I'm assuming it's unlocked. I wasn't sure if there was a prepaid nano-sim I could purchase for each country? If so, which network is best? If possible, I'd love a UK based sim that will work in Paris... As my French is non-existent, so buying one in Paris might be an issue.