If you forgot your phone code, what you can do is to have a hard reset. Hard reset means restoring the phone back to its original factory settings. if you do not do a factory reset, then you cannot change the code. It is the only way that you can change it. But on the other hand, this method deletes everything that you have saved in your phone memory. Including images, contacts, videos and everything on your phone memory. To do a hard reset on your Samsung GT-C6712, do the following steps:
1. Turn on your phone.
2. Open your dialer/dial pad.
3. Type: *2767*3855#
4. If there will be a confirmation message, just choose Yes.
5. Wait for the process to finish.
Note Use the code on your own Risk
you will lose all the contacts and private data
Note: After the hard reset, your phone will automatically reboot itself. If your device freezes after doing a hard reset, just do this: