If a phone is requesting a PIN and the owner cannot remember it, what should they do?

When a phone is requesting a PIN that the owner cannot remember, the appropriate step is to contact the carrier for a PUK (Personal Unblocking Key). This situation typically arises when a SIM card is locked after multiple unsuccessful attempts to enter the correct PIN. The PUK is a unique code provided by the carrier that allows the user to unlock the SIM card. It is integral to regain access to the phone's services without losing any data stored on the SIM.

Other options, while potentially useful in different contexts, might not address the immediate issue effectively. For example, contacting Apple Support is more suitable for hardware or software issues specific to Apple devices, but it might not resolve a locked SIM card situation. Resetting the device could lead to data loss and does not inherently resolve the locked SIM issue. Trying common PIN combinations is not advisable since repeated failed attempts can lead to the SIM card becoming permanently locked, thus necessitating the use of a PUK from the carrier.