Should've been resolved before the plane left the gate. Doesn't matter what 'looks' etc you get. You had a C+ seat. Other pax were in C+ and Econ which makes no sense and leads me to believe they intentionally booked that combination in order to do exactly what they did... get you to move and they get a free upgraded seat. I wouldn't be surprised if they were actually on BE tickets and were just assigned those because thats what was left.