I've taught this to too many people to care enough to argue with you so I'll just tell you to look up the definition of "theism" so you'll know where you went wrong. If you're still trying to argue with me after that, you're clearly either trolling or just too stubborn to admit when you made a mistake.
Theism: belief in the existence of a god or gods. Polytheism: belief in the existence of more than one god. Monotheism: belief in the existence of only one god. Atheism: disbelief in the existence of a god or gods. Agnostic: belief that nothing is known or can be known of the existence or nature of God
For reference, disbelief is the refusal to accept that something is true or real. In this case, that "something" would be "god exists." Agnostics are not atheists, because they hold the position that he might or he might not, and there's no way to know. Atheists refuse to accept the first possibility.
In other words: Atheists believe he does not exist. Agnostics believe he might exist. Theists believe he does exist.
"Refusal to accept" a claim is not the same as claiming the opposite.
I am an atheist because I do not believe that some god exists. You may also call me an agnostic atheist, because I do not claim to know whether or not a god does or does not exist.
You can call me an agnostic if you want, but I'll call myself an atheist. And ultimately, what I think doesn't change regardless of the label someone puts on it.