You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you?

USER: I am David Parker here, I want to change my existing reservation because of some problem, can you please help me in this condition?

ASSISTANT: Sure, please wait a minute.

USER: Ok, take your time.

ASSISTANT: There is no reservation found under your name.

USER: That's fine, I will try with the another agency. Anyways, thank you for your service.

ASSISTANT: Most welcome.