You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Melissa Nelson here.

ASSISTANT: How may I help you?

USER: I just want to change my existing reservation, due to some health issues. Can you please help with it?

ASSISTANT: Sure, please wait for a moment.

USER: Ok, sure.

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

USER: Ok, not a problem. Anyways, thank you for the information.

ASSISTANT: Thank you for reaching us.