。
Take back what you said about me being cheap.
Literal
I [subject-が] cheap [quotative-だと] said thing [object-を] retract-[command-なさい].
けち ('stingy, cheap, petty') is a casual pejorative. だといった marks the quoted characterization with the copula+quotative+said pattern. 取り消す ('to cancel, to retract, to take back') is a compound verb from 取る ('take') + 消す ('erase') = 'take (back) and erase.' ~なさい is a soft imperative.