Help! I do not remember my voicemail pass code and do not want to restore all data

Hi, I recently upgraded from it to an iPhone5 and synced all my information from my old phone to this new iPhone. However my voicemail is now requesting a pass code. I did not have a passcode on the old phone and therefore cannot change my password on this new phone. How do I access the supposed old passcode and then delete the need for passcode without having to restore all data? Thank you for your help.