To write data to a SIM card, press the Write button, or go to SIM -> Write SIM. If multiple card readers are connected to the system, you will be asked which card you wish to write to (the readers that have a SIM card plugged in will be shown with an icon of SIM a card on their left).
Choose a SIM from the list and press OK. A progress bar will illustrate how much of the process is complete.
Some sections of the SIM card are protected with the PIN2; if one such section was modified, you will be asked to enter PIN2.
Enter PIN2 and press OK.
Note. If the code you entered is incorrect, you can try to enter it again. The bottom right corner of the window notifies you how many entry attempts there are left, several (usually three) unsuccessful attempts in a row will block the SIM card (you can unblock it later with the PUK). Keep in mind the fact that the number of attempts is limited; entering an invalid code will decrease the number of attempts by one and change the labels' style to bold red.