You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Patrick Miller here.

ASSISTANT: Do you need any assistance from us?

USER: I want to change my existing reservation today, can you please help me?

ASSISTANT: Sure, I am glad to assist you.

USER: Thank you.

ASSISTANT: Miller, I have't found your reservation in our portal to change.

USER: Ok, that's fine. Anyways, thank you for checking.

ASSISTANT: Thank you for opting us, have a great day.

USER: Most welcome.