I would get the oil at the proper level, have the Mazda dealer look at it, then determine what to do.  I’m thinking that the engine will be ok, but the service manager at the dealership will tell you his experience.  I would get the place that changed the oil to give you some type of warranty in writing, that would cover any engine damage down the road that would have resulted from oil being overfilled.  Keep documents on any maintenance and oil changes from now on.