CESSNA 750 FLC WERE FORGOTTEN BY ARTCC CTLR IN HDOF TO APCH CTL DURING DSCNT RESULTING IN VECTORS TO LOSE ALT NEAR THEIR DEST.

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WE WERE ON CTR FREQ AND ACKNOWLEDGED A DSCNT TO 17000 FT. AFTER SEVERAL MINS WE OBSERVED THE TFC WE HAD BEEN FOLLOWING (AND SLOWED TO 310 KTS EARLIER FOR) DSNDING ON OUR TCASII. AS WE NEARED THE POS AT WHICH THE TFC AHEAD HAD BEGUN ITS DSCNT (APPROX 50 MI NE OF AML VOR) WE ASK CTR (FREQ 132.05) FOR A DSCNT. ATC ADVISED US TO RETURN TO OUR LAST FREQ. I REPLIED 'WE NEVER SWITCHED FREQS;' WE WERE STILL ON THE FREQ IN WHICH WE CHKED ON; AND THEN WERE GIVEN A DSCNT TO 17000 FT FROM FL310. THE CTLR SEEMED CONFUSED AND ASKED OUR POS. I REPLIED '30 DME ON THE 015 DEG RADIAL FROM AML VOR.' AFTER SEVERAL MINS I ASKED IF ATC WOULD LIKE US TO CONTACT IAD APCH. ATC THEN ASKED IF WE WERE LNDG IAD; I ACKNOWLEDGED YES. WE FINALLY WERE HANDED OFF TO THE APPROPRIATE FREQ AND AFTER LENGTHY VECTORS OVER IAD MADE AN UNEVENTFUL LNDG. I THINK WE HAD INITIALLY CHKED ONTO CTR FREQ OF 132.05 AND A DIFFERENT CTLR ACKNOWLEDGED US. I BELIEVE SHORTLY AFTER THE ORIGINAL CTLR WAS REPLACED BY ANOTHER CTLR; AND WE WERE OVERLOOKED BY THE SECOND CTLR. IF THIS WERE THE CASE I THINK THE HDOF PROCS FOR ATC CTLRS WOULD BE A FACTOR IN THIS SIT. I THINK A BREAKDOWN IN COM HAPPENED DUE TO A NEW CTLR TOOK OVER AND THOUGHT THE FIRST CTLR HAD HANDED US OFF TO THE NEXT. HOWEVER; WE WERE NEVER GIVEN ANOTHER FREQ TO CONTACT; UNTIL THE FLC ASKED FOR A LOWER ALT.