pronunciation - Ocha in Hiragana

I'm pretty early into learning Japanese. I've started learning hiragana, when writing "ocha" in hiragana I've noticed it comes up as おちゃ now I know お is "o" and normally ち is "chi" while ゃ is ya. Now my question is why does ocha come out that way? From my early perspective that comes out as Ochiya.

Thanks.