A question to a native speaker of English

I'd probably just say "Oops, you gave me a bit too much!" while handing the extra back to the cashier. Or maybe "I think you might have miscounted." I can't think of a phrase that would be used offhand like we have if a cashier shortchanges us. @owlwings is really good with questions like this, so perhaps he'll be able to help out here.

I would say; "Excuse me, I think that you gave me too much." There isn't really an equivalent idiom to "short change". Many people would use the phrase "short change" as a verb: e.g. "I'm sorry, I think you have short changed me!"

The change is too much. Hope this helps some @yanzalong

I would just say they gave me too much money back. If someone didn't give you back enough change, you could say they short-changed you.

Normally you would tell them that they gave you back too much and return the extra. There is nothing like you over paid your you are shot.