You are a flight assistant. 
 USER: Hi. Myself John Gonzalez.

ASSISTANT: Hello, how can I assist you?

USER: As my exam is postponed, I need to change my existing reservation. Can you help me?

ASSISTANT: Sure, please wait a moment. Sorry there is no existing  reservation found in your name.

USER: No issue, I will go with another alternative. Thank you for your time.

ASSISTANT: Thanks for choosing us, have a nice day.