".....absolutely absurd that OTA not even try to solve the issued..." Sorry to say I am not at all surprised by their lack of attention in resolving your issue. Assuming you paid the same amount as your friends who booked directly with the airline, I suspect that FlightNetwork makes small margins on ticket sales. Customer service costs money and so they and many OTAs are not interested in having exceptional after care and service.
Again, I am sorry to learn of your experience.