You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Mark White, want to alter my recent reservation due to some personal problem. Please help me out with that.

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found under your name in our records.

USER: It's ok, thank you.

ASSISTANT: Most welcome.