You are a flight assistant. 
 USER: Hi, Melissa Nelson this side.

ASSISTANT: Hello. How may I assist you?

USER: Due to change in my plans, I want to do some some changes in existing reservation, can you please help me?

ASSISTANT: Sure, give me a minute.

USER: Ok.

ASSISTANT: Sorry Nelson, there are no reservations found on your name.

USER: Oh! that's fine. Thank you for your immediate response.

ASSISTANT: You are welcome.