Samsung Galaxy S3 is reportedly not available in UAE now, the reason being it is out of stock. The supplies to the big retailers have stopped, and they say they been concentrating more on promoting sales of S4.
Though sources say that some UAE retailers are still selling S3, but on the whole, S3 has been phased out. But you can still catch up on the Android 4.3 update which will be available on S3 soon.