If you're visiting London from abroad, don't forget that the UK dialling code is +44 (which replaces the 0) and to check your own country's code before you travel.
Calls and texts
If you are travelling to London from abroad, using your mobile phone may cost you more than it does at home.
Roaming charges vary between countries, and while travellers from the EU can now use their phones (calls, texts, data) in the UK as part of their home mobile contracts, visitors from further afield will most likely have to pay extra. Check your network's roaming charges before you travel.
If you're planning to stay in London for a significant period of time, consider buying a pay-as-you-go SIM card when you arrive. These are available from any mobile telephone shop and allow you to make calls and send text messages at the local rate.
Using the internet on your smartphone
Most Tube stations are wifi enabled -Transport for London have details.
If you're from outside the EU and want to use a smartphone to browse the internet and receive emails while in London, your network will be charging you extra.
To save money, turn off your data connection before you travel, then head to one of the many internet cafés or venues offering free wifi when you want to check your messages. Be aware that while some hotels provide free wifi, others will charge for this service.
You can also rent a pocket mobile wifi service with unlimited data during your trip.