You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Helen Gonzalez here.

ASSISTANT: How may I assist you today Helen?

USER: I would like to change my existing reservation due to some health issues, can you please me help in that?

ASSISTANT: Sure, I am glad to help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment to check your previous reservation.

USER: Sure, I will wait for your response.

ASSISTANT: We regret to inform you that there is no reservation found on your name in our records.

USER: That's ok, no problem. Anyway thank you for the information.

ASSISTANT: Thank you for reaching us, hope you have a great day.