Can I leave a message?
A question asked when the person one wishes to speak to is currently unavailable. Well, if he's in a meeting, can I just leave a message?
Could I leave a message?
and Can I leave a message?Can I request that a message be written down for a person who is not available to come to the telephone. Bill: Can I talk to Fred? Mary: He's not here. Bill: Could I leave a message? Mary: Sure, I can leave a message for him.