FlyDubai review: booked paid extra 10 kg didn't show in system at airport

Today we are flying from faisalabad airport with you guys, we paid last friday for extra 10 kg luggage and now at the airport they refuse our printed email ticket confirmation and told us to reduce the 30 kg bag to 20kg bag. They called head office in dubai and they were told that they dont have anything in the system regarding our 10 kg extra.
Why?