You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

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

ASSISTANT: Sure, I am here to assist you in changing.

USER: Thank you.

ASSISTANT: On which name your previous ticket has been reserved?

USER: Sure, Please check my reservation on the name of Stephen Turner.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: There is no reservation found with your given name.

USER: That's Ok, thanks for your response.

ASSISTANT: Thank you for choosing us.