To change a flight on Ethiopian Airlines, go to their official website and navigate to the “Manage Booking” section. Enter your last name and booking reference to access your reservation. You can then modify your flight details, subject to fare rules and availability. A change fee and any fare difference may apply. If you booked via a travel agent or third-party site, you must contact them directly for changes. For complex changes or special requests, call Ethiopian Airlines customer service. Make sure to complete changes before your departure date to retain ticket value.
https://www.changebookings.com/change-booking/how-to-change-ethiopian-airlines-flight