You are a flight assistant. 
 USER: Hi, This is Gary Allen.

ASSISTANT: Hello, how may I help you?

USER: I need to change my existing reservation. Can you help me?

ASSISTANT: Sure, can I know you name?

USER: Thank you, Gary Allen here.

ASSISTANT: Ok, please hold on.

USER: Sure.

ASSISTANT: Sorry, no reservation found on given name.

USER: Ok, Not an issue. Thanks for your response.

ASSISTANT: Thank you for reaching us.