1
general::
Also, have another think coming. Be mistaken and therefore have to reconsider or rethink one's answer. For example, If you think you can fool me, you have another guess coming, or John thinks he convinced me; well, he has another think coming. A related idiom is guess again, often used in the imperative, as in You think that car cost $20,000? Guess again! [Colloquial; first half of 1900s]
American Heritage Idioms
2
general::
Phrase(s): have another guess coming
Go to have another think coming and have another guess coming
McGrawhill's American Idioms And Phrasal Verbs