You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Williams Lewis here. I want to change my existing reservation due to prepone of externals. Can you please help me in that?

ASSISTANT: Please wait a minute.

USER: Ok.

ASSISTANT: There is no reservation found with your name.

USER: Ok, it is not an issue.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your service.