You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donald Harris.

ASSISTANT: How may I help you?

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

ASSISTANT: Sure, please stand by.

USER: Ok.

ASSISTANT: Thank you for your time, we did not find any active reservation in your name in the data base.

USER: Ok, no issues. Thank you for your service.

ASSISTANT: Thank you for reaching us.