You are a flight assistant. 
 USER: Hi. I am Sandra Allen.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation due to my convocation dates are postponed.

ASSISTANT: Sure, please wait a moment I will check and revert to you.

USER: Ok.

ASSISTANT: Sorry, I found no reservation in your given name.

USER: Not an issue.

ASSISTANT: Thank you for consulting us.

USER: Thank you for quick response.