[davidshakes]

I was flying Peruvian Airlines from Arequipa to Lima.
I had a window seat, but as I wanted to sit down one guy was already there having ticket for the same seat.
1.My seat was changed without notice
2.Nobody ackknowledged "Sorry, we had to change your seat."
They advised, that if you check in on internet, then you have to ask again by the counter, if your seat is still the same.
By the way, if you are in Peru, arrive to airport at least 1-2 hours before the flight, local airlines might fly much earlier than the time assigned.

[Silent Bob]

Obviously I have never flown peruvian air, but if they are like most airlines, if you checked in at home then the seat you had shouldn't have changed at all. Unless there was an aircraft change, then its definitely the fault of the airline for a) not informing the passengers before boarding that there was an aircraft change, thus seats may have changed and 2) for not realizing that they gave the same seat to two diff people.

Quite an odd one indeed. Not sure whom you can report this two, but if you kept both the original boarding pass, plus your new boarding pass then you should complain to the airline about it.