Can you still get Antenna TV over the air where you live?
Antenna TV is one of those networks, like Decades or Buzzr, that is provided by other TV stations in your area. There's a good chance the station in your area decided, for whatever reason, to replace Antenna TV with Light TV. (I think Albany, NY did this sometime last year.) There was a similar situation in a number of cities where Decades TV got replaced by Start TV, and there are a number of threads here about that.
You can go to the Antenna TV website and see if it is still available in your area. I have a feeling that it is not, in which case, there is nothing Comcast can do about it.
That answers the question, then - Comcast can't show a channel that is no longer supplied to it. You have to find out which station was showing Antenna TV as one of its subchannels, then complain to it.