Oi?

Yes, Oi, as in "Oh darn, oh cripes, oh crud," etc.

Oi, (There it is again,)

-VToE

Generally an English (British english, not American english) phrase, to express shock, disbeleive, surprise, or outrage, generally the latter. Read Harry Potter, as that is the most common example, and pay close attention to Ron's speech; you'll see it.

Am I British? Darn right I am.