If you guess the PIN1 incorrectly three times, the card locks. You will then need the PUK (PIN Unlocking Key) from your carrier. If you enter the PUK incorrectly ten times, the SIM card becomes permanently destroyed and unusable.
Use the software's visual directory tree to expand the Master File and browse individual Elementary Files.
Furthermore, the SIM card maintains a secure file system defined by the ETSI and 3GPP standards. This system consists of , which act as directories, and Elementary Files (EFs) , which are the actual data files storing information such as the phonebook (EF-PBR/EF-ADN), last dialed numbers (EF-LND), SMS messages (EF-SMS), and the preferred network list (EF-PLMNsel). Understanding this hierarchical structure is the first step in mastering any SIM Card Explorer tool.