Hello, I am Michael robert live in the USA and I am a Frequent Traveler. I work for AirTravelPolicy.  

As per  United Airlines Cancellation Policy ,  You can cancel travel up to 24 hours before the scheduled flight departure . If you cancel your reservation, United will refund your purchase, but it may keep 10% of the fare. The Right of Withdrawal does not apply to promotional fares, so please refer to the fare rules for your ticket.

United            Airlines Change Flight , You may be able to change a flight booking through United Airlines even if you booked through a third party. However, you may have to pay the applicable flight change fee. It’s always a good idea to check your options with your source of purchase before making a flight change via United Airlines. .

Check other Airlines policies                                                                

United Airlines Name Change

Delta Airlines Name Change on Ticket

American Airlines Name Change on Ticket

American Airlines Change Flight