Jehovah Winesses: If the name Jehovah is so important why is it never used in the entire greek new testament?

Jehovah is only found in the old testament so how does that make that name more special than the "I AM" which is, which was, and which is to come. I know Jehovah is a name of Sovereign God but don't you think JW's overemphasize since it's not even brought up in the New Covenant? If men edited out the name of God, "YHWH" when they copied the New Testament, as only the Watchtower organization claims, then how can we have any confidence in any of the New Testament? Should we discard the New Testament or the Watchtower organization as unreliable????