You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Christopher Gonzalez. I want to change my existing reservation due to health issues, can you help me in changing the reservation?

ASSISTANT: Sure, we are here to help you. Please give me a moment to check your details in reservation list.

USER: Sure.

ASSISTANT: Thank you for waiting, there is no reservation exist on your name to do modification.

USER: No problem, thank you.

ASSISTANT: Thank you for contacting us.