I don't buy that

American Slang

Definition

An expression indicating disbelief or skepticism; a way of saying you don’t believe or accept what’s being said.

Examples

"He said he missed the meeting because of traffic, but I don’t buy that."

"They claim the app’s new fee is to “improve user experience”—I don’t buy that."

"She swore the dent was already there when she borrowed the car; I don’t buy that."