It's highly unlikely that you've been banned for using a VPN. It's more likely that you had some software on your rig that was found to be illegal, by EvenBalance's standards, whether knowingly or unknowingly.
Unfortunately, as PunkBuster is EvenBalance's technology they have discretion surrounding bans. You will need to obtain a new copy of the game to play again on PunkBuster enabled servers where bans are enforced.
I'd highly recommend you do a clean install of your rig first though.
