Car star 5 second then cut off and radio still running while the car is not running

I been having a problem with my car it is crank and start for 5 second then cut off radio still playing while the car is not running take it to the shop 3 time finally they said it has some to do with ignition switch so I have replace a new ignition switch my car running just fine for a week now it do the same thing a gain.
Any I dear what's wrong with my car?