SIM card usage is restricted in North Korea.
If you are visiting North Korea as a tourist you can have your own SIM card from that country The SIM card wil allow you to use the data plan of the country’s network and it will allow you to access Facebook and Twitter accounts of yourself. But when you leave the country you can’t give it to any person as it won’t work from the date you leave the country.
The SIM card can be activated once you return to the country for another vacation.The deceision was made by the authorities in the month of July . It may be to contoll their citizens from using the data plan to send and receive messages with out any controll over the content.