2000 Hyundai Accent Lock doesnt let me change from P to R o

This problem started few days ago, the button lock doesnt go down and doesnt let me move it, what i do is turn the engine step on the brake and keep pressing it, then turn the engine off, start the engine (pressing the brake) and move change it to R or D; i was told there might be the brake swith that is attached in the pedal, but the thing is that my brake light works, does anyone know what the problem is?
Thanks