Call Of Duty Black Ops 2 Camo Code

I recently preordered the new call of duty game and i received a free ghost camo code. everything went fine but when i didnt see my new camo i came to remember i entered in the wrong gammer tag so i didnt receive my free camo. i have received a new camo code but it will not allow me to access the new code as it says my email has already used a camo code. so i would like to know how i can fix this to use my new camo code and receive my ghost camo that i paid for, thanks in advance.