You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I want to change my existing reservation which is done recently due to some health issues, can you please help me?

ASSISTANT: Please wait for a moment.

USER: Sure, I will wait.

ASSISTANT: Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, no problem. Anyways, my name is Debra Lewis.

ASSISTANT: Thank you.

USER: Thank you for your service.