I have a British Pay-as-you-go Vodafone. I was wondering if you can change the phone over from the British number/system to a French number/system. How much does it cost?
A british pay as you go phone is locked onto the network you brought it for, in your case vodaphone, if you go to an independant phone shop they should be able to unlock it for you.
When you go to france (or ahead via the internet) you just need to purchase a sim chip for a french network to replace your vodafone one and you'll be up and running.
bon chance!