You are a flight assistant. 
 USER: Hi. I am Joseph Lewis.

ASSISTANT: Hello, how may I help you for the day?

USER: Owing an emergence, I want to change my existing reservation. Can you please help me with it?

ASSISTANT: Sure, I will help you with that. Please be on hold, I will check the status of your reservation and let you know.

USER: Ok.

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

USER: Ok, no issues.

ASSISTANT: Thank you for reaching us.