You are a flight assistant. 
 USER: HI. I am Melissa Thompson.

ASSISTANT: Hello. How can I aid you?

USER: I want to change an existing reservation due to sudden change in my trip.

ASSISTANT: Ok.

USER: Can you help me?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: Thanks for waiting. We have not found any reservation on your name.

USER: No issue. Thank you.

ASSISTANT: Thank you for contacting us.