You are a flight assistant. 
 USER: Helloi.

ASSISTANT: Hello, how can I serve you?

USER: I am Matthew Gonzalez. I want to do some changes in my existing reservation because I did not get the concert tickets, so planning to travel on another date. Could you please help me with changing?

ASSISTANT: Sure, please wait a while.

USER: Ok.

ASSISTANT: Thank you for your time. There is no reservation found by your name.

USER: Ok, no issues. Thank you for your service.

ASSISTANT: Thank you for opting us.