Virgin prophecy unfulfilled?

Isaiah 7:14—”This prophecy was not fulfilled by Jesus, since ‘amla’ (sic) is not ‘virgin’ but ‘young lady’, and Jesus was never called Immanuel in the Bible.”

The first objection—that עלמה ‛almâh only means ‘young lady’, is incorrect. It actually refers specifically to ‘maiden’, that is to a young woman who is unmarried and sexually chaste, and thus has virginity as one of her characteristics. So when the Septuagint translators—200 years before the birth of Christ—rendered ‛almâh with the Greek parthenos (a specific term for ‘virgin’) they rightly perceived the meaning of the Hebrew term. Either way, Mary was both a “young lady” and a “virgin.”

The second part of the prophecy is that this child would be called עמּנוּאל ‛immânûêl , which is simply Hebrew for “God-with-us” [It is unclear from the Hebrew whether this is referring to what Mary would call her child or what others would call the baby]. Besides the fact that this title is given specifically to Jesus in the Injīl (Matthew 1:23), Jesus has been known to millions of Christians throughout history as “Immanuel.” So how in any sense could this be an unfulfilled prophecy?