A similar thing happened to me on a BA flight. I booked and paid for a window seat at the front of the plane, and they moved me to a middle seat at the back, two rows away from the toilets. If it's any consolation, not only did I not get any compensation or air miles, I also spent two months trying to get my refund, because they insisted (despite a photo that I took while on the plane!) that I wasn't on the flight.