Here is a quote from Augustine’s Tractates on John where he clearly affirmed that Jesus is the Angel of God who appeared throughout the Hebrew Bible as both God and God’s Angel/Messenger:
7. Lastly, what did those men who saw this miracle think? The men, says he, when they had seen the sign which He had done, said, This is indeed a prophet. Perhaps they still thought Christ to be a prophet for this reason, namely, that they were sitting on the grass. But He was the Lord of the prophets, the fulfiller of the prophets, the sanctifier of the prophets, but yet a prophet also: for it was said to Moses, I will raise up for them a prophet like you. Like, according to the flesh, but not according to the majesty. And that this promise of the Lord is to be understood concerning Christ Himself, is clearly expounded and read in the Acts of the Apostles. Acts 7:37 And the Lord says of Himself, A prophet is not without honor, except in his own country. John 4:44 The Lord is a prophet, and the Lord is God’s Word, and no prophet prophesies without the Word of God: the Word of God is with the prophets, and the Word of God is a prophet. The former times obtained prophets inspired and filled by the Word of God: we have obtained the very Word of God for our prophet. But Christ is in such manner a prophet, the Lord of prophets, as Christ IS AN ANGEL, the Lord of angels. For He is also called the Angel of great counsel. Nevertheless, what says the prophet elsewhere that not an ambassador, nor an angel, but Himself coming will save them; Isaiah 35:4 that is, He will not send an ambassador to save them, nor an angel, but Himself will come. Who will come? The Angel himself? Certainly not by an angel will He save them, except that He is so an angel, as also Lord of angels. For angels signify messengers. If Christ brought no message, He would not be called an angel: if Christ prophesied nothing, He would not be called a prophet. He has exhorted us to faith and to laying hold of eternal life; He has proclaimed something present, foretold something future because He proclaimed the present, thence He was an angel or messenger; because He foretold the future, thence He was a prophet; and that, as the Word of God He was made flesh, thence He was Lord of angels and of prophets. (Tractate 24 John 6:1-14; bold and capital emphasis mine)
Augustine not only affirmed that Christ appeared as the divine Angel of God in his prehuman existence, he also quoted the Greek version (commonly referred to as the Septuagint [LXX]) of Isaiah 9:6 to prove it:
“For a child is born to us, and a son is given to us, whose government is upon his shoulder, and his name is called the Angel of great counsel (megales boules Angelos): for I will bring peace upon the princes, and health to him.”
Compare:
“For to us a child is born, to us a son is given, and the government will be on his shoulders. And he will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace.” New International Version (NIV)
FURTHER READING
Ignatius of Antioch’s Proclamation of the Essential Deity of Christ
Justin Martyr’s Witness to Christ’s essential and eternal Deity
Revisiting Shabir Ally’s Distortion of Justin Martyr Pt. 1, Pt. 2
IRENAEUS AND THE DEITY OF CHRIST
Tertullian and the Doctrine of the Trinity
Answering Islam Blog 
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