Thanks for posting!
Can you let me know what console/platform you are playing on? Also, where was the game purchased? You very well may need to contact your retailer about this.
I also bought the French version instead of the English oine and contacted Activision support and here is what they said to me, the game is only in the language of the box and there is now way for them to issue a replacement or change the language. The only was is to go to the merchant where the game was purchased and get an English copy (that is what I did, thankfully I hadn't opened it yet).
Hope this helps.