If you are traveling to the UK for a short trip, you may be wondering if you can use your cell phone (called "mobile phones" or simply "mobiles" in London). You actually have three choices when it comes to mobile calling in the UK: 1) Activate an international plan with your cell phone provider; 2) Rent an international cell phone; or 3) Purchase an unlocked phone and SIM (Subscriber Identity Module) card that works in another country.
Speak to your current phone company to see if they know which UK SIM cards will work in your handset.