You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I oblige you today?

USER: I need to change my existing reservation as my exams got postponed, Can you please help me with that?

ASSISTANT: Sure, can I know your good name?

USER: David Thomas here.

ASSISTANT: Please stand by.

USER: Sure, I will wait for your response.

ASSISTANT: Thank you for waiting, there is no active reservation found with the given name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for opting us.