Most mobile companies have a facility called international roaming. This often has to be requested as the service usually needs to be enabled on the handset remotely by the phone company. International roaming call charges can be very expensive, so it's worth checking prices carefully before deciding to go with this method of communication. Within Europe roaming charges ended on 15 June 2017. Europeans travelling within the EU countries can Roam Like at Home and pay domestic prices for roaming calls, SMS and data. Three is the only UK network which includes an extended list of countries outside the EU on it's 'Feel at Home' facility (see below).
Global SIM cards are an option and we list a number of providers in our resources below.
For many other countries it may be better to buy a local SIM card for your existing phone, or rent or buy a handset once in the country to achieve the cheapest solution. You can research this before you go ... look for a network provider in your destination country with PAYG, 'top up', 'non-subscriber' or 'prepaid' options if you don't want a long term contract. These are usually much cheaper than 'roaming' SIMs. This means that other local contacts can easily call you too. Some providers are listed in our resources below.
For advice about using mobile phones outside the UK, try the following: