iPhones can only be unlocked by the carrier to which they were originally locked. You would have to contact that carrier to see if you qualify for an Unlock.
Also, the iPhone's warranty is only valid in the country where the phone was originally purchased. If the phone is from the United States, all repairs/service/replacement must be done there; the warranty is not valid in Saudi Arabia
Your iPhone was locked to a carrier and hacked to get it to work with another carrier, and updating the iPhone removed the hack and relocked the iPhone to the original carrier. The Grevey SIM is illegal in almost every country in the world and use of one may well have voided all possibility of support from either Apple or your cell carrier.
But you can try calling AT&T and asking if you can get your iPhone unlocked; only they can do so. AT&T can be reached at 1-800-331-0500; it will be up to you to find one of the several ways of calling a US 800 number from other countries.