[Open] it's not my account

[Julia.]

Maybe one of you made a typo if your keys are quite similar. Besides that you shouldn't be asked for your game-key by any server, just by the game itself.
There should be an option to change the key used on your copy, as well, some use multiple keys while playing with the same steam-acc and only change the warband-key used to launch. If you don't know how, I can ask someone who I know from that he did it.