Hyundai i30 2009: Gearbox problems

The 2009 Hyundai i30 automatic wagon I recently bought has a couple of gearbox problems. It changes from second to first with a very noticeable clunk, and the motor revs out when changing from second to third and from third to fourth, although the changes are smooth. Two mechanics have told me that only Hyundai can fix the problems, as it is a software issue. Further advice is that not all Hyundai Dealers have this software equipment and I could waste a lot of money just getting the gearbox serviced. The problem was noted at 30,000 km, but nothing was found, and the car has now done 45,000 km. Can you please advise me where to take the vehicle to get it serviced and the software update done?