Có cái lồn
A Vietnamese swearing phrase that is used to express the doubt or the disbelief to the information you receive, or that is another way to say "No!", meaning you do not want to do something.
A : Ê, cô giáo gọi cho bố mẹ mày về vụ mày trượt bài kiểm tra rồi đấy. (Hey dude, the teacher, she called your parents and told them you've failed the test.)
B: Có cái lồn tao tin. (I ain't believe you.)
B: Có cái lồn tao tin. (I ain't believe you.)