Welcome to FlyerTalk.

First, you must deal with Flight Centre as your arrangements were booked through them.

If it was all booked on one ticket, but with many sectors & carriers, and there was a flight to/from the US, then the DoT ruling applies. This is applicable to every nationality, not just US citizens.

For members to post any thoughts on your situation, it will be very useful if you can provide the details of the the route. You seem to describe a number of return flights, each to or from the US.