have another guess coming, to

have another guess coming

(One's) expectations are wrong and unreasonable; (one) better think again. Almost always preceded by "If (one) thinks (something)." If you think you can walk in here and just demand a raise, you've got another guess coming. If he thinks he can hit it big without paying his dues, he's got another guess coming.
See also: another, coming, guess, have
Farlex Dictionary of Idioms.

have another guess coming

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]
See also: another, coming, guess, have
The American Heritage® Dictionary of Idioms by Christine Ammer.

have another guess coming, to

To be wrong or mistaken. This phrase also implies that though one is wrong, one has a chance to reconsider and correct one’s error. It dates from the first half of the 1900s. C. Day Lewis used it in Child of Misfortune (1939): “If you think that’s your doing, you’ve got another guess coming.”
See also: another, guess, have
The Dictionary of Clichés by Christine Ammer
See also:
  • have another guess coming
  • have another thing coming
  • you've got another thing coming
  • you've got another think coming
  • You’ve got another think coming
  • quit (some place)
  • quit a place
  • go against the flow
  • What are you on?
  • never in a month of Sundays