Most mobile phones on the market today come with some form of user security. This means the phone can be set up so a password or PIN number must be entered before using the phone's features. In situations where phone users have forgotten their password or PIN, it is highly dependent on the phone manufacturer and carrier whether the phone is recoverable. If a password or PIN is entered incorrectly multiple times, the SIM card locks, and the phone will cease to function. Some phones have a PUK (PIN Unlock Key) that only the carrier and manufacturer have access to.
Contact your carrier and ask if they can provide you with the PUK (PIN Unlock Key). Some carriers charge a fee for this, and others will not unlock the phone until the end of the contract.
Insert a new SIM card. If the phone cannot be unlocked, purchasing a new SIM card will prevent you from having to buy an entirely new mobile phone.
Wipe your phone of data and revert to factory settings. Some phones, including the iPhone and other smartphones, have a feature to wipe the phone. This reverts the phone back to factory settings and will result in the loss of any data on the device. If your phone does not use a SIM card, this may be your only choice to recover the phone.