O2 is a cellphone network owned by Telefónica, a Spanish telecommunications company. The network is available in several European countries, including the United Kingdom and Republic of Ireland. You can switch your existing cellphone number to the O2 network should you decide to change service providers. This is helpful because it means you do not have to tell your social or business contacts about a change of number. Moving your cellphone number is uncomplicated but can take several days.
Contact O2 (see Resources) or visit an O2 store. Sign up for a "Pay As You Go" or "Pay Monthly" contract. You will need an existing account with O2 to transfer your telephone number.
Contact your existing cellphone network. You need a Porting Authorizing Code (PAC) in order for O2 to transfer your number. In order to get a PAC code you will need to fulfil any outstanding contractual obligations with your current service provider.
Give your PAC code to O2. The code contains three letters and six numbers. It is usually valid for 30 days after issue. O2 will give you a date for your phone number transfer. You will receive a text message on your old number as a reminder.
Wait until you lose signal on your O2 phone. This is normal and means your number is being transferred. Keep your phone switched off, turning it on periodically over the next few hours until a signal is detected. Once you can get an O2 signal on your phone your phone number has been successfully moved.