You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I address you?

USER: I want to change my existing reservation due to postpone of my exams, can you help me with that?

ASSISTANT: Sure, on which name your previous ticket has been reserved?

USER: Barbara Walker.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: We did not find any reservation on your given name.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Thank you for opting us.