Let me Echo BOBNSPIKE's words: Simply put, Nowhere in the USA do you change to departure without being advised by tower (military aside). no where do you switch frequencies in normal situations without being handed off to a new frequency.
I've been based at DCA/IAD/BWI for about a dozen years. It is a demanding place to fly. Simply put, ATC screwed up big time.
22 years ago, I was cleared for ILS 9R apch and cleared to land on 9R at KPHL. No problem right? Except ATC kept saying there was departing traffic on 27LEFT.
I kept asking what on earth they had planned for us. HALF A DOZEN times I asked what was going on. ATC kept saying it would work out ok and seperation would be assured.
WELL IT WASnt, so we were going down the GS in vmc at the same time a DC10 was climbing straight towards us...we actually DUCKED UNDER THE DC10 (we were in a DC9)
3 controllers were decertified on the spot.
NEVER trust anyone...
IT is sad to say, that every generation seems to have to repeat the misakes of the past.