Can I have (one) call you?
Can I take a message now and ask the person you wish to speak to (who is unavailable) to call you back later? He's in a meeting right now, so can I have him call you?
Could I have someone call you?
Could I take a message so your call can be returned? (A question asked by someone who answers the telephone when the person the caller is seeking is not available. The someone can be a person's name or a pronoun, or even the word someone. Also used with can or may in place of could.) Tom: Bill's not here now. Could I have him call you? Bob: Yeah. Ask him to leave a message on my machine. Tom: Sure. "Could I have her call you?" asked Mrs. Wilson's secretary.