O2 is a global systems for mobile communications cellular service provider in the United Kingdom. As a GSM cellular service provider, O2 cellular devices require a subscriber identity module to function. This SIM card allows O2 to identify you when you use the O2 cellular network. You can activate your O2 SIM card by inserting the SIM card in your phone and calling O2's customer service department from your mobile phone.
Insert the O2 SIM card in your O2 mobile phone. In most cases, you will insert the SIM card under the phone's battery. Once you insert the SIM card, replace the battery and back cover on your O2 phone.
Power on your O2 phone.
Dial "202" from your O2 mobile phone and press the "Send" button.
Tell the customer service representative that you would like to activate a new SIM card. If you do not currently have an O2 account, the customer service representative will ask you some basic questions such as your name, national identity number, address and phone number.
Select a calling plan and calling features. The customer service representative can explain the currently available service options.
Wait while the customer service representative completes the activation process. After finishing your call with the O2 customer service representative, you will receive a text message confirming activation of your SIM card. This process can take up to 24 hours, but will usually occur within two hours. You can now use your O2 SIM card to make and receive telephone calls and text messages and access O2's cellular data network.