United Airlines offers the facility to make changes in your flight bookings. Pessengers will have to pay United Airlines Change Fee if their ticket is restricted. Change fee is fully dependent upon route and destination. Pessengers will have to pay $200 for changes in domestic flights and $400 for the flights under the international flight category. You have so many ways to make changes but pessengers mostly choose the online method through go to the website of airline's then selecting the flight then paying the applicable fees.

https://airlinespolicy.com/flight-change-policy/united-airlines-change-policy/