You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Jeffrey Thomas.

ASSISTANT: How may I assist you today?

USER: I want to alter my reservation, due to postponement of concert to be held at the place where I wanted to visit, can you please take your some time for helping me?

ASSISTANT: Sure, give me a minute.

USER: Ok.

ASSISTANT: Sorry Thomas, I couldn't find any reservation on your name.

USER: No issue. Thank you.

ASSISTANT: Welcome.