The Nokia 106 is renowned for its durability, long battery life, and extreme simplicity. While it doesn't run a smartphone OS, it does operate on a basic Series 30+ (or similar) platform that responds to USSD codes (often called "secret codes" or "MMI codes").
Use these tools responsibly—they are great for testing a used phone's hardware or resetting it before passing it on. How to Use Secret Codes on NOKIA 106