开房: check in

退房: check out

存房: keep

开房

A: Hi,there,may I help you with check in?

B: Yeah, thank you

A: My plesure

退房

A: Hello, you wanna check out?

B: Yes,.....

存房

A: How are you today?

B: Fine, thank you, I wanna keep my room for ? more day/s.

A: Ok,....

大致就是这样啦,这些是比较口语化的,语法没有按照规则,不过老外都这样说的啦,希望可以帮到你.