W350i support

Before you can make or receive calls, you must turn on your phone and be within range of a network. When you turn on the phone, it automatically selects your home network if it's within range. If it's not, you can use another network (provided your network operator has an agreement that allows you to do so). This is called roaming.

Some phone models switch automatically between GSM and 3G (UMTS) networks depending on availability. Some network operators allow you to switch networks manually, because searching for unavailable networks consumes battery power.

You can make a phone call by entering a phone number (with international country code and area code, if applicable) and pressing the call key or "Call", depending on your phone model.