How do I fix my locks for my car doors?

I took my Ford Explorer XLT 2002 to a mechanical engineer to fix my tires and my a/c. But, I think they've been messing with my car doors. Because now instead of locking my doors with the on on the side of the door, I have to lock it with my hands. So, does anyone know how to fix it, because I am not taking it to another mechanical engineer and paying another lke $100-$200.