Just looking of some JAX sector charts, 128.70 (north) and 127.95 (south) are depicted in the same sector, so the same controller will be working both frequencies all the time. Just listening to the feed now I see they have also merged in the CAE area sector on 124.70 and FLO area sector on 133.45, so you would have to program those frequencies in as well to hear the aircraft. That configuration might be a weekend thing, not used during the week ?