It is not a true statement. Jesus was called "Son of God" on several occasions and even Jesus Himself called Himself "Son of God" in many places. Let us see some Bible verses where Jesus was called, "Son of God."

Jesus heard that they had cast him out; and when He had found him, He said to him, "Do you believe in the Son of God?" He answered and said, "Who is He, Lord, that I may believe in Him?" And Jesus said to him, "You have both seen Him and it is He who is talking with you." Then he said, "Lord, I believe!" And he worshipped Him.

(John 9: 35-38)

Again we see in John 10:30 that Jesus said, "I and My Father are one." Then the Jews tried to stone Him and Jesus asked, "why you want to stone me?" We read the answer of the Jews in John 10:33, "For a good work we do not stone You, but for blasphemy, and because You, being a Man, make Yourself God."

When Jesus heard that Lazarus was sick He said, "This sickness is not unto death, but for the glory of God, that the Son of God may be glorified through it." (John 11:4)

When Jesus returned to the house of Lazarus He says to Martha :

"I am the resurrection and the life. He who believes in Me, though he may die, he shall live. "And whoever lives and believes in Me shall never die. Do you believe this?"

She said to Him, "Yes, Lord, I believe that You are the Christ, the Son of God, who is to come into the world."

(John 11:25-27)

Angel tells Marry

Before the birth of Jesus when an angel appeared to Marry in her vision, she was told that one who is to be born will be called the Son of God.

And the angel answered and said to her, "The Holy Spirit will come upon you, and the power of the Highest will overshadow you; therefore, also, that Holy One who is to be born will be called the Son of God.

(Luke 1:35)

Devil said to Jesus, If you are the Son of God

Jesus fasted for forty days and night and the tempter came and said to Him, if you are the Son of God…

But He answered and said, "It is written, 'Man shall not live by bread alone, but by every word that proceeds from the mouth of God.'"

Then the devil took Him up into the holy city, set Him on the pinnacle of the temple,
and said to Him, "If You are the Son of God, throw Yourself down. For it is written: 'He shall give His angels charge over you,' and, 'In their hands they shall bear you up, Lest you dash your foot against a stone.'"
Jesus said to him, "It is written again, 'You shall not tempt the LORD your God.'"
Again, the devil took Him up on an exceedingly high mountain, and showed Him all the kingdoms of the world and their glory.
And he said to Him, "All these things I will give You if You will fall down and worship me."
Then Jesus said to him, "Away with you, Satan! For it is written, 'You shall worship the LORD your God, and Him only you shall serve.'"
(Matthew 4:4-10)

Many a times when Jesus went before devil possessed people, demons cried out and testified that He is the Son of God as we read in these verses. They trembled before the Son of God and came out from people.

When He had come to the other side, to the country of the Gergesenes, there met Him two demon-possessed men, coming out of the tombs, exceedingly fierce, so that no one could pass that way.

And suddenly they cried out, saying, "What have we to do with You, Jesus, You Son of God? Have You come here to torment us before the time?"

Now a good way off from them there was a herd of many swine feeding.

So the demons begged Him, saying, "If You cast us out, permit us to go away into the herd of swine."

And He said to them, "Go." So when they had come out, they went into the herd of swine. And suddenly the whole herd of swine ran violently down the steep place into the sea, and perished in the water.(Matthew 8:28-32)

Also we read that whenever unclean spirits saw Him they fell down and cried out, "you are the Son of God."

And the unclean spirits, whenever they saw Him, fell down before Him and cried out, saying, "You are the Son of God." (Mark 3:11)

People testified it

Not only did the devil, demons or angels proclaim that Jesus is the son of God but also many people also testified that He is the Son of God.

And when the disciples saw Him walking on the sea, they were troubled, saying, "It is a ghost!" And they cried out for fear.

But immediately Jesus spoke to them, saying, "Be of good cheer! It is I; do not be afraid."

And Peter answered Him and said, "Lord, if it is You, command me to come to You on the water."

So He said, "Come." And when Peter had come down out of the boat, he walked on the water to go to Jesus.

But when he saw that the wind was boisterous, he was afraid; and beginning to sink he cried out, saying, "Lord, save me!"

And immediately Jesus stretched out His hand and caught him, and said to him, "O you of little faith, why did you doubt?"

And when they got into the boat, the wind ceased.

Then those who were in the boat came and worshipped Him, saying, "Truly You are the Son of God."

(Matthew 14:26-33)

Likewise the chief priests also, mocking with the scribes and elders, said,

"He saved others; Himself He cannot save. If He is the King of Israel, let Him now come down from the cross, and we will believe Him.

"He trusted in God; let Him deliver Him now if He will have Him; for He said, 'I am the Son of God.'"

(Matthew 27:41-43)

And Jesus cried out again with a loud voice, and yielded up His spirit.
Then, behold, the veil of the temple was torn in two from top to bottom; and the earth quaked, and the rocks were split, and the graves were opened; and many bodies of the saints who had fallen asleep were raised; and coming out of the graves after His resurrection, they went into the holy city and appeared to many. So when the centurion and those with him, who were guarding Jesus, saw the earthquake and the things that had happened, they feared greatly, saying, "Truly this was the Son of God!"

(Matthew 27:50-54)

Miscellaneous

Mark wrote in the very first verse of the Gospel of Mark that, Jesus is the Son of God. "The beginning of the gospel of Jesus Christ, the Son of God." (Mark 1:1)

Therefore, when the chief priests and officers saw Him, they cried out, saying, "Crucify Him, crucify Him!" Pilate said to them, "You take Him and crucify Him, for I find no fault in Him." The Jews answered him, "We have a law, and according to our law He ought to die, because He made Himself the Son of God."

(John 19:6-7)

But these are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in His name.