If their on two unmerged accounts...Thats it. Nothing more. Anet has a strict "we can't merge acconuts after they've been activated" policy.
When you created the account, it was very clear what you were doing (Theres plenty of confirmation screens, and its clear which you are doing) so its near impossible to not merge them if you meant to merge them.
If you didnt want them merged then, and changed your mind now...your out of luck