TICKETS SWOP SERBIA

I HAVE JUST RETURNED FROM HOLIDAY TO FIND I HAVE BEEN SENT ONE ADULT AND ONE CHILD TICKET FOR THE SERBIA GAME(LOWER) . I ASKED FOR TWO ADULT TICKETS. I HAVE NOW BEEN TOLD THAT THERE IS NOTHING THEY CAN DO. IF ANYONE WANTS TO SWOP FOR TWO ADULT TICKETS FOR THESE. I WILL OBVIOUSLY PAY THE DIFFERENCE.
CHEERS