there has not been raised up anyone greater than John the Baptist....and if you want to accept it, he himself is Elijah who is destined to come. (matthew 11:2-14)
Stop reading the New World Translation and get yourself a regular Bible. That alone would clear up a whole lot. Let's look at Matthew 11:14 in a few regular translations:
NASB - 14 "And if you are willing to accept it, John himself is Elijah who was to come.
NIV - 14 And if you are willing to accept it, he is the Elijah who was to come.
KJV - 14 And if ye will receive it, this is Elias, which was for to come.
NLT - 14 And if you are willing to accept what I say, he is Elijah, the one the prophets said would come.
You see, John The Baptist (Elijah) was prophesied about in the OT. (Malachi 3:1, Matthew 11:10). So Matthew 11:14 is confirming that John The Baptist was in fact the prophesied return of Elijah.