There are a couple more interesting points from Jeremiah 28 that Wasblind referred to in his excellent post.
(verse 15)
And Jeremiah the prophet went on to say to Hananiah the prophet: “Listen, please, O Hananiah! Jehovah has not sent you, but you yourself have caused this people to trust in a falsehood.
How many times has Watchtower done that? 1914, 1925, 1975, the 'generation', there are only a 'few remaining months til armageddon' etc. All of these are now known to be "falsehoods" that all of Jehovah's Witnesses trusted in.
(verse 9)
As regards the prophet that prophesies of peace, when the word of the prophet comes true the prophet whom Jehovah has sent in truth will become known.
Watchtower claims to be God's true prophet* today, but no prophet can be a true prophet until his words come true. A long list of Watchtower's predictions have already failed. None have come true. There is no way the Organization can be taken as a true prophet.
*The Society claims to be a true prophet
(W 4-1-72, p197)
“So, does Jehovah have a prophet to help them, to warn them of dangers and to declare things to come?
“These questions can be answered in the affirmative.
“This prophet was not one man, but was a body of men and women. It was the small group of footstep followers of Jesus Christ, known at that time as International Bible Students. Today they are known as Jehovah’s Christian witnesses. They are still proclaiming a warning, and have been joined and assisted in their commissioned work by hundreds of thousands of persons who have listened to their message with belief."