There are many companies which sell Mobile with sim locked condition.  AT&t sell many samsung, lg, htc, iphones with sim locked condition. T-mobile also sell many of samsung galaxy, lg stylo , iphone and htc mobile in sim network locked condition. In Canada bell and telus sell gsm cdma mobile in locked condition. Sprint and Verizon sell lg cdma samsung cdma mobile in locked condition.

                       When gsm mobile is sim locked you cannot use any other sim on that mobile.  For example if your mobile is locked with o2 sim you cannot use orange sim without unlocking your smartphone. You must unlock your mobile. Similarly when cdma mobile is network locked you cannot use other network unless you unlock cdma mobile. Cdma mobile do not use sim , so network information are stored as software coded so unlocking cdma mobile is bit difficult compare to gsm mobile. Now a days there are also unlock codes for cdma mobile unlocking otherwise installing custom rom is the best way to unlock cdma mobile.

                 If your mobile is sim locked and you insert new sim to that mobile without unlocking than you get one of following message on your smartphone screen - network locked sim card inserted, wrong invalid simcard inserted, sim or phone restricted, enter restriction code, enter unlock codes or contact service provider.

                       Many of mobile company motorola, htc , lg provide free bootloader unlock code file. These can be done only with fewer model of motorola, htc , lg.

For that visit bootloader unlocker support page on respective mobile website.

                     Then you need to provide device id of your android smartphone. Device id is different from imei number of your mobile phone. Device id is of 64 to 128 characters long.

To find device id of your android smartphone. There are some different code for different mobile phone.

1) You first install adb and fastboot application on your computer.

                      You can get adb and fastboot application under sdk – software developer kit . So first download sdk file. Under android studio you can also find sdk tool.

                    Unzip sdk tool. Open sdk manager file. This will give you list of packages included under sdk. Unselect all and select only 1) android sdk tool and 2) android sdk platform tools. These are normally first two options. Adb and fastboot tool are include under sdk tools.

Now click on install package and accept license. Continue installing software.

2) Enable usb debugging mode on your android smartphone which you want to sim network unlock.

3) Also install usb driver for your mobile.

4) Now type    adb devices      on command prompt.

5) This will give you list of android devices attached to computer. If you can’t find your device in that list than recheck that you have installed proper usb driver for your mobile and usb debugging is on under developer option of your smartphone.

6) Now reboot your mobile in bootloader or fastboot mode.

7)type command      adb reboot bootloader    to reboot in fastboot mode.

8) Your mobile reboot in bootloader/ fastboot mode

9) Now enter command       fastboot oem device-id.        This command work for lg mobile.

If you have motorola mobile than use this command      fastboot oem get_unlock_data.

If you have htc mobile then use this command           fastboot oem get_identifier_token.

10) After getting device-id go to that lg htc motorola mobiles bootloader unlocking support site.

11) It asks for your mobile device id and your email id etc.

12) If your mobile is eligible for unlocking than you will get unlock key to your email id.

13) To unlock your mobile enter following command

Fastboot oem unlock  {your unlock key that you received to your email for free}. This command is used for unlocking motorola mobiles.

For lg mobile unlocking type        fastboot flash unlock  {unlock.bin  file that you received at your email id}.

For htc mobile unlock type                  flash unlocktoken   {unlock_code.bin file that you have got at your email id for htc unlocking}. 

       You will get warning message that unlocking bootloader can void your warranty. Click yes to continue.

Now type     adb reboot bootloader

Then type     getvar all

You will get message that bootloader unlocked : yes or device is unlocked.

                  Many company sell Unlock sim adepter attachment to unlock your sim card. This sim adapter is like small thin pcb circuit size same as your smartphone’s sim card slot. This sim card unlocker adapter is placed at sim slot of your mobile and on the top of that sim adepter you put your new sim card. Then it will not ask for sim network unlock code or sim restriction code. This unlock sim card adapter can used with many mobile like lg mobile samsung mobile even you can use with iphone 6 iphone 4 and many other iphone unlocking. This can work with t-mobile sim, at&t sim unlocking, roger sim unlocking and many other gsm sim.

Method 3 using cable and box for mobile unlocking via usb and rj 45.

                        You can get unlocking box having usb and rj 45 connector. But this boxes are mostly associated with particular mobile brand for example if you have samsung unlocking box than it can used for unlocking many samsung galaxy mobiles but it cannot unlock lg mobile htc or sony ericson mobile. Similarly if you have lg unlocking box that you can unlock many of lg mobile only. This is best for mobile network unlocking shops. For single mobile unlocking this is not a good option.

                         This can unlock some older mobile but it is not working for latest mobile and this is not guaranteed method to unlock mobile. If mobile is locked at bootloader level then installing fresh Stock Rom or custom rom does not unlock your mobile.

                       This can only unlock mobile if sim locking is done at software firmware level. You can download stock rom or custom stock rom from internet. But make sure it is stable and genuine. Do not download from any unreliable sources.  You must download stock rom as per your mobile model number.  Lg samsung galaxy motorola’s each model have different stock rom version. So be careful while downloading stock rom.

1)You require flash tool for installing stock rom. Normally flashing tool including with your stock rom and if there is no tool under stock rom then separately download tool from internet.

2) Install usb driver for your mobile phone on laptop computer.

3) Install flashing tool on your computer.

4) Copy stock rom folder on your computer.

5) Open flash tool application and click on scatter loading tab.

6) Then give path to your stock rom folder and under stock rom folder open firmware.

7) Under firmware folder find a file having  android_scatter name. Normally name of this file is model number of your mobile + android scatter.

 Scatter file has list of loading sequence on your android phone.

8) Now click on scatter file and it will load all the sequence.

9) Now click on download tab under flash tool. Once it loads 100 percentage at the same time remove battery from your mobile and connect it to computer via usb port.

10) Tool started installing stock rom on your mobile and once it installed completely you get green signal under flash tool.

                       Mostly cdma mobile are locked at software level. So installing custom rom can unlock mobile. Installing original stock rom may not unlock cdma mobile as it is original stock rom from company itself.

                       There are many free unlock code generator application available. To generate unlock code for smartphone you need following information about your smartphone.

Once you generated unlock code enter new sim to your mobile. It will prompt for sim network unlock pin, enter nck code. Some of the sim require both nck and spck code to unlock mobile and some of samsung mobile need defreeze code and nck code for unlocking mobile.