You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I need to change my reservation as my plan to go for trekking got postponed. Can you help me?

ASSISTANT: Sure, we are here to help you. May I know your name please?

USER: Thank you. I am Charles Harris.

ASSISTANT: Sorry to inform you that there is no active reservation on your given name.

USER: Ok fine, thanks for your response.

ASSISTANT: Thank you for contacting us.