You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,.

USER: I am Deborah Thomas.

ASSISTANT: How can I assist you?

USER: I need to change my existing reservation, as my exam scheduled got postponed. Please help me in changing?

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: No reservation exists.

USER: Ok, no issues.

ASSISTANT: Thanks.

USER: Thank you for your service.