You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: My name is Melissa Collins. I want to change my existing reservation, can you please help me in doing that?

ASSISTANT: Please wait a moment, let me check with your details.

USER: Sure.

ASSISTANT: Sorry, there are no active reservations to change on your name.

USER: No problem, thank you for your time.

ASSISTANT: Thank you for reaching our service.