退房: check out
存房: keep
開房
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,....
大致就是這樣啦,這些是比較口語化的,語法沒有按照規則,不過老外都這樣說的啦,希望可以幫到妳.