cambiar, verb:
to change
You can use cambiar in several different ways, which broadly parallel how you use to change.
No has cambiado nada.
You haven’t changed at all.
Quiero cambiar este abrigo por uno más grande.
I’d like to change this overcoat for a bigger one.
Notice how you use de in these phrases:
Tenemos que cambiar de tren en Guadalajara.
We need to change trains in Guadalajra.
He cambiado de idea.
I’ve changed my mind.