Welcome to FT!
The airline (presumably QR) takes control over ticket from 48-24 hours before departure, so by then you can contact QR directly for rebooking. Otherwise, go to the airport for check-in and let the ground staff deal with it (airport stafff has much more leeway to rebook than if you call QR). Most likely you will be put on the next available QR DOH-KUL flight; it is easy to fix and shouldn't be an issue. i.e. you shouldn't be too concerned.
PS. You should have posted this in the QR forum.