Does 3G or 4G work in a different country?

I live in Mexico, and I have an iPhone 5s and I'm going back to the states for a few months. Will I be able to use 3G as I'm there? Like in the area where I don't have Wi-Fi?

I have a friend from england who visited the states and whenever she tried to use her phone off Wi-Fi, it would say there was no SIM card inserted. Also, when i visited canada with my father, his phone would switch carriers every half hour while we were over the border. So it might work, i can't say for sure

More than likely though I wouldn't suggest you do cause that would result in heavy roaming charges.

  • Will my iPhone 5 work in a different country? It's an iPhone 5, and I live in NZ. We're going on a trip to America for a couple of weeks, and I don't know if my phone will work. I don't care if I can't text or make phone calls, or about roaming or whatever with Vodafone. I just want to make sure I can use Wi-Fi like usual. Obviously the camera and iPod parts will work? But what about Internet? Cheers.
  • Why when you buy IPhones from different country you need to have it unlocked? My friend told me that if i'm buying my phone from States and bringing it to asia i have to wait for 2 years for it to unlock why is that?
  • When in a contract, can I get a different SIM while in another country? I'm going to china in 15 days and I want an IPhone so I can take pictures and have data while I'm there. I'm staying for an entire month. Getting this IPhone (with either sprint or T-mobile) with put me in a 2 year contract. Will I be able to use my phone while I'm there with the new SIM card I'm buying in China. I heard that my phone will be locked while I'm out of the country or something.
  • Using Viber on iPhone with Wi-Fi in different country? Hi so I'm traveling next week and I was wondering if it will be free to use Viber from my iPhone using Wi-Fi. If I'm connected to Wi-Fi will I be charged/ will it work in a different country. I'm going to America if that matters.