2003 Impala Headlights and interior lights

I have a 2003 Imapala with 117,000 miles on it. It has a 3400 v6 in it. When I turn the engine off and take the key out of the ignition. The headlights and the dash lights and the radio stay on. They will not shut off. I have changed the ignition swith, but this did not fix the problem. I have also changed a couple of relays which also did not fix the problem. Any help would be appreciated.