I should think not

I should think not

I would naturally expect that this would not happen or be true. A: "Don't worry, you won't have to pay for the additional service." B: "I should think not, seeing as I never agreed to it in the first place!"
See also: not, should, think
Farlex Dictionary of Idioms.

I should think ˈso/ˈnot

(also I should think she, etc. ˈis/ˈdoes/ˈdid, etc.) used for emphasis when agreeing that something is right or correct: ‘He didn’t give the waiter a tip.’ ‘I should think not, after such bad service.’ ‘He finally apologized for what he said.’ ‘I should think so.’ ‘I’m very angry with my son.’ ‘I should think you are. He’s behaved very badly indeed.’
See also: not, should, think
Farlex Partner Idioms Dictionary
See also:
  • not for a second
  • (I) hope not
  • hope not
  • not for a minute
  • not for a moment
  • not for a instant
  • not for a/one minute/moment/second/instant
  • aint
  • ain't
  • by no means