You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you today?

USER: Could you please help me to change an existing reservation as my trip got postpone due to my health issues?

ASSISTANT: Sure, I will aid you with that. Can you please mention your name for further process?

USER: I am Sandra Clark.

ASSISTANT: Ok, please hold on a moment.

USER: Sure.

ASSISTANT: There is no previous reservation available under your name.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for reaching us.