You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How glad that I can assist you?

USER: I need to change my existing reservation, can you please help me with that?

ASSISTANT: Sure, I can help you. Can I know your name for checking in our previous booking list?

USER: Ryan Collins here.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: Thank you for being on hold, I have checked with your information in my portal to change your booking but it is displayed that there is no user name found to change it.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: You are welcome and have a nice day.