You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Can you help me to change my reservation?

ASSISTANT: Sure, I am here to help you. Can I have your name please?

USER: My name is Eric Robinson.

ASSISTANT: Ok, please wait a minute while I am checking your ticket status.

USER: Sure, take your time.

ASSISTANT: Sorry for the trouble which is caused to you, I haven't found your ticket in the confirmation chart list. So, I am unable to modify.

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

ASSISTANT: Thank you for the positive response. You are welcome.