If you want to make ammendments to your bookings then you will have to pay Qatar Airways Change fee. You can make changes through the ticket office, call center, or at an airport desk. You can change the date or destination as per your plans. if you are making a delay for the changes then you will be charged by extra fee or penalty.

https://airlinespolicy.com/flight-change-policy/qatar-airways-flight-change-policy/