You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Betty Turner here.

ASSISTANT: How may I assist you today?

USER: Due to sudden health issue, I am not able to travel in a flight on those date that I want to travel. So, I would like to change my reservation. Can you please help me out with that?

ASSISTANT: Sure, please wait a moment.

USER: Thank you for considering my request, take your time.

ASSISTANT: We found your details with us, can you please mention new airport codes?

USER: Sure, I will prefer IAH and OAK as my origin and destination airports respectively.

ASSISTANT: May I know your new travelling dates?

USER: My departure is on Feb 26 and please book my return ticket also on Feb 28.

ASSISTANT: Do you need any specifications for your travel?

USER: I would like to departure in evening time.

ASSISTANT: May I know your connection limit?

USER: I will prefer single connection for my journey.

ASSISTANT: Please wait a moment.

USER: Sure, take your time.

ASSISTANT: Sorry, there are no flight tickets available with your requirements.

USER: Oh! Sad to hear that. Anyway, I will reach another booking agency. Thank you for the information.

ASSISTANT: Thank you for reaching our service.

USER: Welcome.