@AnonymousHave you tried to activate the sim? https://www.o2.co.uk/help/phones-sims-and-devices/activating-your-sim
If you are having problems give customer services a call and ask for a new one https://www.o2.co.uk/contactus
Or if close to an O2 store , pop in there...
*The Game Is On*
All UK mobile numbers start with 07
It will be on the packaging.
Just top up to start using it https://www.o2.co.uk/help/pay-as-you-go/topping-up
Track usage, upgrade and get support with the My O2 appDownload My O2