Wiktionary
say again
phr. (context idiomatic colloquial English) "What did you say?" or "Repeat what you have said." (non-gloss definition: A polite formula used when one has not heard or understood what has been said).
Usage examples of "say again".
I heard the seraphim say again, and her voice sounded uncomfortably like Lady Schrapnell’.
Chewning, we'll match velocities with you in thirteen, I say again one-three, minutes.
Drop everything you have on the intersection of Williams Street and Kenmore, say again Williams and Kenmore, over.