You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I want to change my existing reservation due to some health issues, can you please help me out?

ASSISTANT: Sure, will you mention your name for checking the reservation?

USER: Sure, my name is Brian Allen.

ASSISTANT: Please give me a moment.

USER: Ok, I will wait.

ASSISTANT: Thanks for waiting, there is no reservation found under your name.

USER: Ok, no problem. Anyways, thank you for your service.

ASSISTANT: Welcome, have a great day.