Frustrated client

We booked international flights through Flight Centre. We need the return leg of our flight to be changed and have been calling for weeks to try and change it. The flight is next week and the call centre consultant, Clinton, keeps passing the buck and sending us to the airline who keeps sending us back to Flight Centre. As the travel agent who we did the booking through surely they are meant to be the ones to make the relevant changes and not involve us as the clients in the nitty gritties of the back office works. We are frustrated now as time is of the essence now.