From December 2016, after shut down12 milion falsely registered Sim cards, the government do strictly to enforce all the Sim cards have to be registered officially. The rules is you have to show your Passport and your photo to buy a prepaid Sim card before it can be actived. Small independent corner shops can't activate them for you and they still sell a SIM on somebody else's identity to you. You can still buy a SIM card at a corner store or at the airport. But have in mind that they are not properly registered and you may risk that your SIM will be shut off anytime without prior warning. Even at airport booths, they still sell them without the legal registration. When you ask for it, they will smile or find an excuse or simply lie to you)