In eGO, we have multiple divisions based around specific games or genre of games. When a member joins eGO, they need to select a home division as they're promotions/demotions are handled by that division's leadership. So for you, the advisors and division leaders of Call of Duty will be the ones responsible for tracking your progress as a member, and promoting/demoting you, which is deemed fit (no, you cannot be demoted from e, except to be just kicked out, which only happens if you break eGO rules, such as no racism).
That does not mean you cannot have fun and play with other members from other divisions. We encourage all members to have fun and meet and make new friends. It's not uncommon to see DOD:S division members playing CS with TF2 division members. Likewise, you'll catch WoW division members in a Strat room playing Minecraft with CoD members.
eGO is unique and special in this regard as the only limitation imposed on you is how you're promoted and who's responsible for the promotions. Besides tha, you can take advantage of the wide spread offering of different game servers and players that this clan has. And yes, if you feel that you would be a better member in a different division, you are allowed to change. Just be sure you inform your current division leadership (advisor) via a private message notifying him of your planned transfer, and the new division's leadership you will be joining.
Hope this helps.