No one denies that he is one. My point is that you seem to be basing your view on logic; you don’t see how it is logically possible for God to be both three and one at the same time, so you deny it. But the thing is, lots of things about God are illogical, I only pointed out one there are countless others. If we use only human logic to judge everything about God then we’d be in a big mess. That’s what we’re trying to get at, that sometimes you just have to take a leap of faith, and trust that God’s revelation is true and let go of reason and logic for a moment. We believe in the Trinity because we believe God has revealed to us that it is true. If God came to you and told you it was true, would you believe him? Or would you deny it because you see it as illogical?
God speaking: Simple, either all three persons of the Trinity spoke at once or only one person spoke, depending on the context of the passage.