Why can't i download Annihilation map pack for call of duty black ops?

well theres a few things it could be it may not be in your country yet or try getting on the computer go to xbox.com log in find the add on by searching or browsing and then purchase it online and if all else fails sometimes game stop carries cards that have a number on it for you to type in and unlock the add on so you could bye it their and if its not in the store then you should always be able to get the virtual one gamestop.com for your 360 good luck man