You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me?

ASSISTANT: Please wait a moment.

USER: Sure, I will wait.

ASSISTANT: Can you please mention your name.

USER: Sure, my name is Stephen King.

ASSISTANT: Sorry, Stephen King there are no active reservations found on your name.

USER: Ok, that's fine. Anyways, thank you for your service.

ASSISTANT: Thank you for choosing our service.