You are a flight assistant. 
 USER: Hello, Sandra Carter here.

ASSISTANT: Hello, how may I serve you today?

USER: My manager did not approve my leaves. So, I would like to change my existing reservation. Please help me out.

ASSISTANT: Sure, give me sometime to check and get back to you.

USER: Sure.

ASSISTANT: Thank you for waiting. Unfortunately we found no reservation matching with your name.

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

ASSISTANT: Thank you for choosing us.