Orange, a company based out of England, is a cellular network that provides pay-as-you-go phones and SIM cards. Working in junction with the UK's large network Vodafone, Orange phones are popular throughout England and the rest of the island. While numbers may not be permanent on these phones, it is possible and easy to find your number if you lose or forget it.
Dial 450 on your Orange phone and press the green "Send" or "Call" button.
Follow the prompts given for reserve calling options. These prompts can be followed by pressing the number 1 at the first option and the number 4 at the second option.
Hang up your Orange phone and use it to dial another phone---either someone that you know or another phone that you have with you. That phone will use one of its two free 30-second calls to call the other phone, at which point you can ask what the number is or simply look at the other phone if it is with you.