or the switch? this is the only problem, the steering wheel is not locked it moves freely.

How badly is the key worn? Try a new key cut by code from the dealership. If you get a copy of a bad key you will be in the same boat. A new key is cheaper than a cylinder. (Worth a try) If the new key does the same thing then replace the cylinder.

try a different key moving it up and down while turning.if this dont work,replace the switch.