The Nokia 800 Tough is unlocked for international use and can be used with any GSM network worldwide that supports the frequency or band used by the device. However, it will not work with CDMA networks such as Verizon, Sprint, or Boost. The wireless frequencies for 3G, 4G, and LTE differ by network, and even if the device supports them, it may require a new SIM card or additional configuration, and network coverage may vary depending on location. If you have any questions about compatibility, please check with your carrier.