Talk To Me In Korean just did a video on a phrase I always use in English!
I TOLD YOU SO!!!
Here's a really quick quide to how to say it in 4 different ways:
Informal Language (to friends)
내가 그랬지? (nae-ga keu-raet-ji?)
I told you so, right?
내가 뭐랬어? (nae-ga mweo-rae-sseo?)
What did I tell you?
Formal Language (to people you don't know well)
제가 말했잖아요? (jae-ga mal-haet-jya-na-yo?)
Didn't I say that?
제가 말했죠? (jae-ga mal-haet-jyo?)
I said that, right?