BE02 ACFT (2) WITH SIMILAR CALL SIGNS. APPARENTLY THE CTLR CONFUSED THE TWO AND DIDN'T REALIZE THEY BOTH HAD ANSWERED TO A DSCNT CLRNC. SEPARATION WAS LOST AND RPT FROM CTLR INDICATES HE WAS CHARGED WITH AN OPERROR.

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APPROX 10 MINS AFTER DEPARTING ORH; ZBW CLRED US DIRECT TO CCC AND THEN TRACK THE CCC R-221 OUTBOUND TO INTERCEPT J-121. ASSIGNED ALT WAS FL220. BEFORE XING CCC (WITHIN 10 NM) CTR CLRED US TO DSND TO FL200. DURING THIS DSCNT WE CROSSED CCC; AND GOT ESTABLISHED ON THE CCC R-221. WHILE DSNDING THROUGH FL205 WE WERE CLRED TO CONTINUE OUR DSCNT TO 15000 FT AND GIVEN A FREQ CHANGE AT THE SAME TIME. THE FREQ WE WERE LEAVING WAS VERY BUSY AT THIS TIME; AND AB123 WAS ALSO ON THE SAME FREQ (OUR CALL SIGN WAS AB223). AS WE CONTINUED OUR DSCNT THROUGH FL200 WE NOTICED TFC ON THE TCASII AT THE 12 O'CLOCK POS AND LESS THAN 1000 FT BELOW US. WHILE LISTENING FOR A CHANCE TO CHK IN ON THE NEW FREQ; WE HEARD CTR GIVING ANOTHER ACFT VECTORS AND THE REASON FOR THE VECTORS WAS AN ACFT DSNDING TO 15000 FT WHO WAS ON THE WRONG FREQ. ASSUMING THE CTLR WAS REFERRING TO US; WE SLOWED OUR RATE OF DSCNT AND ATTEMPTED TO VISUALLY ACQUIRE THE ACFT AS WE WERE NOW ISSUED A TCASII TA. AT THIS TIME WE WERE AT FL194. IMMEDIATELY AFTER GIVING THE OTHER ACFT THE VECTOR; THE CTLR ON THE NEW FREQ CONTACTED US AND STATED 'CTR NEEDS YOU BACK ON THE PREVIOUS FREQ.' WE RETURNED TO THE PREVIOUSLY ASSIGNED FREQ; AND CHKED IN WITH THE CTLR STATING THAT WE WERE DSNDING OUT OF FL190 FOR 15000 FT. AT THIS TIME WE WERE CLRED TO STOP OUR DSCNT AT FL180. APPROX 10 MINS LATER; ZNY ADVISED US THAT 'THERE MAY HAVE BEEN AN ATC DEV AND TO REMEMBER THE SPECIFICS.' THROUGHOUT THE FLT; AND SPECIFICALLY DURING THIS INCIDENT; ALL ATC CLRNCS WERE READ BACK WITH OUR FULL CALL SIGN AND FLT NUMBER IN ACCORDANCE WITH COMPANY PROCS AND THE AERONAUTICAL INFO MANUAL.