Jailbreaking a mobile phone, such as a Casio Hitachi G'One, means to unlock the SIM card so that it can be used with any service provider. So, if you have Verizon service and would like to switch to AT&T, you will need to jailbreak the phone. The good news is that there are online sites that will generate unlock codes, and you don't have to know much about electronics in order to input the codes in your phone.
Open your Web browser and navigate to a site that provides unlock codes for the G'zOne mobile phone. Enter your phone model in the information box.
Turn off your G'zOne and slide the battery cover off of the rear of the unit. Remove the battery and locate the IMEI number printed on the battery sticker and note it.
Enter the IMEI number into the unlock generator when prompted. It costs money to generate an unlock code, so you will be prompted to enter your payment info.
Enter your payment info and confirm the purchase. The unlock code will be sent to the email address you provide.
Note the unlock code, replace the battery in your phone and turn it on.
Enter the unlock code as you would dial a number and press "Send." The phone will then unlock, and you can use any SIM card you like in the phone.