You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Gregory Lopez here.

ASSISTANT: What type of service you are expecting from us?

USER: Due to some personal issues, I would like to change my existing reservation. Please help me out.

ASSISTANT: Sure, I am here to help you with that.

USER: Thank you.

ASSISTANT: Please wait for a minute.

USER: Sure, take your time.

ASSISTANT: Sorry to say that, there is no active reservation found on your name in our database.

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

ASSISTANT: Thank you for reaching us.