You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Christopher Moore.

ASSISTANT: How can I help full to you?

USER: I want to change my existing reservation due to the postponement of my schedule.

ASSISTANT: Sure, I am gleeful to help you. Please give me a moment to check it.

USER: Ok, sure.

ASSISTANT: I am sorry to say that there is no previous ticket booking found the name which you have provided to modify it.

USER: It's ok, it might be not done properly at the time of booking. Anyway thank you for the information.

ASSISTANT: Most welcome.