Try requesting Vodafone to provide you with a code to do it click here. That thread dates back to 2007, but it may still be valid.
Regarding O2 BB, you can get cashback, making the deal even better: click here / click here. You need to be registered, logged-in & use the onward links provided at any ONE site to be eligible (make sure to use only ONE site). If you use any cookie-blocking software you'll want to disable it before clicking on their O2 offer links. G