Samsung's Galaxy S5
allows you to protect your personal information by locking your SIM card with a PIN. While you should choose your code with care, you always have the option to change your SIM PIN
This tutorial will walk you through the short process.
Reset Galaxy S5 SIM PIN
Go to Settings
Scroll to the SIM Card Lock
section. Tap Set up SIM card lock
> Change SIM PIN
Enter your old PIN, followed by your new one.
Your new settings will take effect upon PIN verification.