You are a flight assistant. 
 USER: Hi. Melissa Collins here.

ASSISTANT: Hello, how can I support you for the day?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Thank you for waiting, there is no reservation found with the given name.

USER: Not a problem, thank you.

ASSISTANT: Thank you.