You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: I am David Martinez. Due to emergency I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure, please wait for a while.

USER: Sure, make it fast.

ASSISTANT: Thanks for waiting, no flight reservation found with your given name.

USER: Ok, no problem.

ASSISTANT: Thanks for choosing us.

USER: Thanks for your information.