Bought second hand Samsung F400 today - it has a pass code set

If your looking at your phone screen and it’s asking you for a security code, you may want to try the last 4 digits of your cell phone number, that is the default for most phones. If that does not work then you can try 9999 or 0000. Those are also standard with most phone companies. If after that you still have no luck, call your service provider to get help with the code otherwise you risk locking your phone out permanently which stops you from being able to receive phone calls, text messages, etc. I’m sorry your having so much trouble with this! I hope I was able to help you today!