Questions I have About Jesus

[XTruthSeekerX]

Matthew, Chapter 1

18: Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost.
19: Then Joseph her husband, being a just man, and not willing to make her a public example, was minded to put her away privily.
20: But while he thought on these things, behold, the angel of the Lord appeared unto him in a dream, saying, Joseph, thou son of David, fear not to take unto thee Mary thy wife: for that which is conceived in her is of the Holy Ghost.
21: And she shall bring forth a son, and thou shalt call his name JESUS: for he shall save his people from their sins.
22: Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying,
23: Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
24: Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife:
25: And knew her not till she had brought forth her firstborn son: and he called his name JESUS.

What Prophet said this and where is it written?

Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying,
Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.

Why did they call him Jesus instead of Emmanuel if spoken of the Lord by the prophet, saying, they shall call his name Emmanuel?