This is a Family Practice. All of the sudden I am getting denials for such codes as 93000 ( EKG)and 71020 ( Chest x-ray). The denial is N265, N286-- Missing or invalid provider #. Up until now my #'s have been correct on my claims. We have changed nothing in our practice. I have called Medicare and they are no help. Has something changed?? Is there anyone else having this problem??