You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Due to my health issues I would like to change my recent reservation which I have done last week to Denver.Can you help me to change my existing reservation?

ASSISTANT: Sure, may I know your name to check your reservation is existing or not?

USER: Deborah Wilson here.

ASSISTANT: Wilson, there is no reservation found under your name to do modifications in that.

USER: It's ok, not a issues.

ASSISTANT: Do you want any other help from us?

USER: No, thank you. Thanks for your valuable information.

ASSISTANT: That's ok, thank you for choosing us.