Different country, different mobile phone technology. Phone networks vary across the world, and a phone that works in one country might not work in another. Sometimes networks in a foreign country don't support certain frequencies, or worse still, they use an entirely different transmission system.
But you're in luck. The site www.willmyphonework.net can help you find out if your mobile device will work at your travel destination. Simply input your device's manufacturer, brand and model, as well as the mobile network carrier in the destination country.