You must remember that Christ was not in Greece. The Greek Septuagint was not written at the time of Christ, but after it.
The people in Judea spoke Hebrew and thus Christ's name would have been the Hebrew pronunciation as Yahshua. Our English version of the New Testament was derived from the Greek and not the Hebrew, thus the confusion.
Absolutely WRONG! The Septuagint was translated in 323 BC, in response to the Hellenization of the known world by Alexander the Great. People completely lost their Hebrew, except perhaps the rabbis, and in some cases not even then.
I DO read both Hebrew and Greek. The fact is, GOD ordained the Greek language to be used to communicate the gospel in the 1st century AD. It was the lingua franca, and people spoke it from Spain to Persia, and south and north, too! It was one of the signs that the time was ripe for the incarnation, crucifixion and resurrection of Jesus Christ.
The reason the name "Jesus" is used is because the Germanic scholars were the original ones to start translating the Bible from Greek. Their "Y" was pronounced "J". And so the tradition has continued.
I do find Ἰησοῦ in my Greek Bible, from Matt 1:1 to Revelation 22:21
"Βίβλος γενέσεως Ἰησοῦ χριστοῦ υἱοῦ Δαυὶδ υἱοῦ Ἀβραάμ." Matt 1:1
"Ἡ χάρις τοῦ κυρίου Ἰησοῦ μετὰ πάντων." Rev. 22:21
Actually, the word "Jesus, or if you prefer, Ἰησοῦς in the nominative case, is found 1058 times in the New Testament.
I just know I never call Jesus by his Hebrew name, because it does not appear in that form in the Hebrew Old Testament. And Ἰησοῦς is a little bit foreign, since I was a Christian for over 30 years before I learned Greek.
I think it is our heart relationship with Jesus that counts.
PS. People in Judea in Jesus time spoke Greek. The common people also spoke Aramaic. Hebrew was reserved for the synagogues, and most people didn't understand a word, just like when the Catholic Church foisted Latin on the world till only a few decades ago. Interestingly, the Orthodox Church always used the vernacular, until they came to North America, and continued to use the vernacular, which only the old immigrants understood, not their grandchildren or children. They lost most of their congregation that way.
So it is a safe bet to say that speaking in your heart language, the name of Jesus is the way to go. That is why they translate Bibles into different languages. So people can relate with their hearts to God.