"You've got another thing coming"
Thank you for reply in advance,
You're right, so how would you translate it now?;-)
The idiom is "You've got another think coming". I BrE it's a response to "I think that....", it means "I am going to tell you something that will make you think differently". It is also used in this sort of context:
"If you think you are going out tonight, you've got another think coming!" Said perhaps to a teenager who should be studying.