You are a flight assistant. 
 USER: Hello. Catherine Collins here.

ASSISTANT: Hello, can you please tell me how may I aid you at this moment?

USER: I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me?

ASSISTANT: Ok, sure.I can search for you with that. Sorry, no reservation found on your name.

USER: That's ok.

ASSISTANT: Thank you for contacting us.

USER: Anyways, thank you for your time.

ASSISTANT: You are welcome.