You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me?

ASSISTANT: Sure, I will help you. Please help me with your name.

USER: Sure, my name is Katherine Carter.

ASSISTANT: Please allow me a minute.

USER: Sure, I will wait.

ASSISTANT: Thank you. Katherine Carter, I am really sorry to inform you that there is no reservation found on your name.

USER: Ok, not an issue.

ASSISTANT: So, I could not make any changes as per your request. Thank you for understanding.

USER: Anyways, thank you for your service.

ASSISTANT: Thank you for reaching us. Have a great time.