Maffu, welcome to the Forums.
Were you able to setup your Blackberry Internet Service (BIS) account with Orange? If you PIN was rejected, it is likely because the previous user has not released the PIN for use again. You should contact the seller and request they do so. If they won't, you can try contacting Orange and asking them to do so.
I assume you have a BlackBerry Data Plan for your Orange account: What do I need a Data Plan for? - BlackBerryFAQ