I have no idea why you think there is such a thing as an unbreakable code that is not a one-time use code.

I have no idea why you think there isn't. Maybe you're going off a strange definition of "unbreakable". When it's used in cryptography, it means "unbreakable in reasonable time limits" (e.g. millions of years).

The thing about good encryption is that it's not just hard to break, it's mathematically too hard to break even if your available computing power keeps rising exponentially. Unless there is a mistake in the algorithm, it is for all intents and purposes, unbreakable.