Hi,
Well, I actually do not know if this was an op-up or not.. but what i know was that the flight was overbooked..
And yes, I did not state all the fact that I was booked in Q class and because of the rerouting I have now a Y-class ticket.
Anyway, I think it is clear that those 3 500-miles taken from my account was not a mistake, and would just blame it on myself for not being so experience on such things.. so lesson learnt.. but not too bad an upgrade.. with the nice purser..
Thanks all for the info.