I say

Từ điển Oxford Advanced Learner 8th

ˌI ˈsay idiom
(old-fashioned, BrE, informal)
1. used to express surprise, shock, etc.
•I say! What a huge cake!
2. used to attract sb's attention or introduce a new subject of conversation
•I say, can you lend me five pounds?
Main entry: ↑say_idiom