"미리(in advance) 말해주지 그랬어요(You should have told me; implying why didn't you?)."
You should have told me in advance. (VERB + -지: when the situation was not what the speaker was expected/wanted with some resentment)
가: 오늘 제 생일이에요. (Today is my birthday.)
나: 미리 말해주지그랬어요. (You should have told me.) 그러면 선물을 준비했을 텐데... (Then I would have got you a gift.)