I don't know what you think you're accomplishing by saying "nuh uh" like this. You've done it a few times, and I don't understand, in any of these cases, why you think anyone would think you'd say otherwise.
If you'd care to elaborate beyond, "nuh uh", I'm sure we'd all be glad to hear it.
If you'd care to elaborate beyond, "nuh uh", I'm sure we'd all be glad to hear it.