You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you today?

USER: Due to health issues, I need to change my recent reservation. Please help me with that.

ASSISTANT: Sure, I am here to help you with that.

USER: Thank you.

ASSISTANT: Can I know your name, to check your status of reservation?

USER: I am Helen Martin.

ASSISTANT: Ok, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on your name in our database.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us.