One moment, please
An expression asking someone to wait patiently for a short amount of time. A: "Hello? Is anybody there?" B: "One moment! I'm just getting dressed." A: "Yes, hello. May I speak to Mrs. Robertson?" B: "One moment please. I'll see if she's available."
One moment, please.
Please wait briefly. (A polite way of acknowledging that you noticed someone's request.) John: Can you help me? Clerk: One moment, please. I will be with you shortly. Bill (answering the phone): Hello? Bob: Hello. Can I speak to Tom? Bill: One moment, please, (handing phone to Tom) It's for you. Tom: Hello, this is Tom.