Security Code

it is the last 4 numbers of your pcs phone number

If you still have a Sprint account (at least, my SPH-A640 was a Sprint), call 18882114727 for technical support. I was treated very pleasantly by the representatives. They can help you momentarily switch your account's service back to the SPH-A640 so you can reset the phone to factory defaults. You can then immediately switch your service back to your current cell phone. It's simple, there's no charge and it will take you just ten minutes to get around that dumb security code.