Could I tell him who's calling?

and Can I tell her who's calling?; May I tell him who's calling?

a question asked by people who answer the telephone to find out politely who is asking for someone. (Him or her can be replaced by a person's name or by a plural pronoun.) Mary (on the phone): Hello. Could I speak to Bill Franklin? Sally: Could I tell him who's calling? Mary: It's Mary Peters. Sally: Oh yes, he's expecting your call. I'll get him for you.