You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: Myself Sandra Williams, I want to change my existing reservation. Can you please help me for this?

ASSISTANT: Sure, I will help you. Please wait, let me check your reservation status in our database.

USER: Sure, I will wait for your kind response.

ASSISTANT: Sorry Sandra, I have not found any reservation under your name in our database.

USER: Not a big deal, anyway thank you very much for you kind service.

ASSISTANT: You are welcome and thank you for reaching us.