DC9 FLC GIVEN INCORRECT FREQ BY ZNY CTLR.

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ON A SCHEDULED FLT FROM MSP TO PHL. WE WERE FLYING THE 'BUNTS ONE ARR' (HAA.BUNTS1) GOING INTO PHL. WE WERE WITH ZNY ON FREQ X. WERE LEVEL AT FL180. WE WERE ASKED TO CHANGE OUR XPONDER CODE. APPROX 1 MIN LATER WE WERE GIVEN FREQ Y; ZNY. THE FO WAS FLYING; I WAS THE CAPT; AND MAKING THE RADIO CALLS. I CHANGED TO FREQ Y AND CHKED IN WITH CTR. I WAS ACKNOWLEDGED BY NYC. WE PASSED OVER HARRISBURG VOR MAINTAINING FL180. I HAVE FLOWN THIS SAME ARR MANY TIMES IN THE LAST FEW MONTHS. I KNEW FROM EXPERIENCE THAT THIS IS A BUSY FREQ TO LISTEN TO. I REMARKED TO THE FO THAT THE FREQ WAS UNUSUALLY QUIET. BY NOW; WE WERE APPROX 10 MI FROM LANCASTER; PA; (VOR) LRP. I XMITTED TO CTR ASKING 'ARE YOU STILL THERE?' I GOT A REPLY FROM THE CTLR 'YES; WE'RE STILL HERE; AND I'M ENJOYING THE QUIET.' SO; WE CONTINUED ON THE ARR TOWARDS LANCASTER (LRP) AND PHL. AFTER PASSING LANCASTER VOR; I BECAME UNEASY; AND THOUGHT WE SHOULD BE GETTING A LOWER ALT. I ASKED FOR LOWER FROM THE CTR. A NEW VOICE SAID 'I DON'T HAVE ANYTHING ON YOU; WHAT IS YOUR POS?' AFTER GIVING OUR POS; THE CTLR SAID; GO BACK TO YOUR PREVIOUS FREQ. I TRIED BUT NO REPLY. I NEXT CALLED PHL APCH AND GAVE OUR POS AND ALT. WE WERE GIVEN ZNY FREQ Z. AFTER CALLING THEM; WE WERE GIVEN A 180 DEG TURN BACK TO LANCASTER; FROM WHERE WE DID ANOTHER TURN ON VECTORS (ALL AT FL180) TO START THE ARR AGAIN. FROM WHAT I COULD GATHER; AFTER OUR NEW XPONDER CODE AND NEW CTR FREQ WE TALKED TO THE WRONG CTLR. WE WERE LED TO BELIEVE WE WERE ON THE CORRECT FREQ. I BELIEVE IT WAS ANOTHER CASE OF OVERCROWDED FREQS. WHEN I READ BACK OUR NEW FREQ CHANGE NOBODY PICKED UP ON THE WRONG FREQ. IT WAS NOT UNTIL I QUERIED ABOUT GETTING LOWER DID WE GET BACK TO THE CORRECT CTR FREQ.