You alway get two codes with your provided SIM card. When booting your phone, you have to enter the PIN (4 digits) to unlock the card and use it. For safety reasons, after 3 failed attempts your card gets locked, in case someone else got your phone and tries to use it.
If your card is locked and you boot your phone, you should get a message on the screen, telling you to enter your PUK (8-12 digits) code. That is the second code you receive with your SIM card. Entering this one will unlock your card again und after that you can use your PIN again.
If you also manage to enter the PUK wrong 3 times, you´re in a bad situation. You have to contact your provider (Vodafone in this case) and tell them what happened. If you´re lucky, they support SuperPUK, another code to unlock your card in such cases. Otherwise, they will send you a new card and you´ll have to pay for it.
If they have have send you the wrong code for sure, you should tell them on the phone. Maybe they´ll send you a new card with the correct code for free.
