The following is from http://www.clayjones.net/2010/08/a-question-the-jehovah%E2%80%99s-witnesses-can%E2%80%99t-answer/
Christian: Let me ask you only one question and after you answer it, I’ll answer any question you want. First I need to clarify a few things. In the New World Translation, John 1:1 reads: “In [the] beginning the Word was, and the Word was with God, and the Word was a god.” Then in Isaiah 9:6 (NWT) we read: “For there has been a child born to us, there has been a son given to us; and the princely rule will come to be upon his shoulder. And his name will be called Wonderful Counselor, Mighty God, Eternal Father, Prince of Peace.” So then, does Jehovah equal almighty God?
JW: Yes.
C: Now Jesus isn’t Jehovah, right?
JW: That’s right.
C: Jesus equals a Mighty God?
JW: That is correct.
C: Is Jehovah a true God or a false God?
JW: Jehovah is a true God.
C: Is Jesus a true God or a false God?
JW: Jesus is a true God.
C: Okay, here’s my question: How can you believe there are two true Gods when the Bible says there is only one God? After all, it says in Isaiah 43:10-11 (NWT), “Before me there was no God formed, and after me there continued to be none.” And Isa: 44:6 (NWT) says: “I am the first and I am the last, and besides me there is no God.”
JW: That passage is teaching that there are no capital “G” gods.
C: Hebrew doesn’t have capital letters so the capitalization of the “G” in those passages is an insertion by the NW translators to make us believe there are two categories of gods. It is equivalent to their just inserting the word “almighty” in the text. If the Lord had wanted to proclaim that “besides me there is no Almighty God” instead of what it really says, “beside me there is no god,” He could easily have had Isaiah insert the word “Almighty” in those passages. But He didn’t.
JW: Well, we only worship one God.
C: If I only loved one wife but was married to two women, I would still be a polygamist and your believing there are two true Gods even though you only worship one of them still makes you a polytheist. The Bible says there is only one God.
JW: But the Bible calls Satan a God.
C: Is Satan a true God or a false God?
JW: A false God.
C: You still have two true Gods.
JW: But in Ex. 4:16 (NWT) it says that Moses “will serve as God to him [Pharaoh].”
C: It says Moses will serve “as God.” In other translations of this verse it says Moses will be “like God” to him. Do you see a difference between serving “as” God or “like” God and really being a god? For example, if I said an older woman was “as a mother to me” it wouldn’t mean that I actually came out of her womb, right? Do you see the difference?”
JW: But the word “God” is just a title that can be used for those on the side of God.
C: Then there would be lots of true Gods, but John 17:3 (NWT) says “This means everlasting life, their taking in knowledge of you, the only true God, and of the one whom you sent forth, Jesus Christ.” If that’s true, how could you say that Jesus is a true God?
JW: As I said, we only worship one God.
C: But I’m not asking about how many Gods you worship, I’m asking about how many Gods you think are true. Can you think of a time when someone says that ‘X’ is the ‘only true’ ‘X’ that it doesn’t make everything else in that category false? If there God is the ‘only true’ God then any other god must be a false god, but you have already said that Jehovah and Jesus are both true Gods and that makes… count them… two true Gods.
JW: 1 Cor. 8:4-6 says “…there is no God but one. For even though there are those who are called ‘gods,’ whether in heaven or on earth, just as there are many ‘gods’ and many ‘lords,’ there is actually to us one God the Father, out of whom all things are, and we for him; and there is one Lord, Jesus Christ, through whom all things are, and we through him.” See, the Father is God, not Jesus.
C: But you’ve already agreed there are two true Gods and this passage says there is only one God.
JW: You’re talking about the Trinity.
C: No, I’m pointing out that Jehovah’s Witnesses are polytheists who believe there is more than one true God, even though the Bible tells us there is only one true God.
JW: We didn’t come here to argue. [What?]
C: Okay, well, if you want to bring someone back, I’ll be glad to talk with them. [That hasn’t happened yet.]