Unlocked Sim Card

After you purchase and use your cellphone for an extended period of time, you can change networks. However, the phone that you're currently using may not be offered on that network. If you wish to keep using your current handset but use another network, you must unlock your phone. This means that you unlock the phone to accept another subscriber identification module. The SIM card itself isn't unlocked.

Sim Cards

Most cellphones you buy have SIM cards installed in them. SIM cards are memory chips used in cellular devices to store your account's information, your cellphone number, your phone book, text messages and other data. Because they contain such sensitive information, avoid removing them from the phone unless absolutely necessary.

Locked SIM Cards

Unless you specifically purchased an unlocked phone, your phone is likely to have a SIM lock on it. This feature prevents you from taking a particular provider's phone and using it on another network. The lock helps keep devices on their originally assigned networks. However, most devices can be unlocked using a SIM unlock procedure.

Unlock Procedure

You can remove the SIM lock by performing an unlock procedure on the phone. Although the specific unlock instructions differ according to your phone model, the procedure consists of obtaining an unlock code from your existing mobile provider. You can also buy a code online if the provider is unable to give it to you. After you obtain the unlock code, you install another network's SIM card, power on the phone and then enter the unlock code when prompted.

Compatibility

Just because you unlock your phone doesn't mean that you can use the phone on any network. The SIM card for the new network must compatible with the network your phone currently supports. The major networks -- T-Mobile, AT&T, Verizon and Sprint -- are either GSM or CDMA networks. Therefore, if your phone is a GSM phone, you can't use it on the Sprint network, as Sprint operates a CDMA-based network.

There are many kinds of unlocked sim card in stock.

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