B727-100 CREW DSNDED AFTER HEARING A DSCNT CLRNC CONSISTING OF ONLY THE LAST 2 NUMBERS OF THEIR CALL SIGN; AND NO COMPANY NAME.

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AT 15000 FT WITH A FREQ CHANGE FOR ZDC. I CHKED ON WITH THE CTLR AND AFTER MY FIRST AND SECOND 'CHK ON' XMISSION WE HEARD 'CD; DSND TO 11000 FT.' OUR CALL SIGN WAS 'ABCD' SO I CALLED BACK TO CTR 'ABCD DSNDING OUT OF 15000 FT FOR 11000 FT.' WHEN WE WERE DSNDING THROUGH 13500 FT; THE CTLR QUERIED US FOR OUR ALT. WHEN WE RESPONDED 13500 FT; HE TOLD US TO CLB BACK UP TO 14000 FT. WE COMPLIED WITH HIS CLRNC AND CLBED BACK TO 14000 FT. LATER; WE HEARD ANOTHER ACFT WITH THE LAST 2 NUMBERS (CD) IN HIS CALL SIGN. WE ASSUME THIS WAS THE BIGGEST REASON WHY THIS HAPPENED. I FIGURE THAT THE OTHER ACFT BLOCKED MY CLRNC READBACK TO CTR FOR DSNDING; THEREFORE; CTR NEVER HEARD MY XMISSION THAT WE WERE DSNDING. THIS RESULTED IN AN ALTDEV. SUPPLEMENTAL INFO FROM ACN 572122: HE TOLD US TO MAINTAIN 14000 FT AND TURN L IMMEDIATELY TO 360 DEGS. HE SOUNDED EXCITED AND GAVE ANOTHER ACFT AN IMMEDIATE TURN ALSO. THIS WAS OUR FIRST INDICATION THAT OUR DSCNT FROM 15000 FT TO 11000 FT MAY HAVE BEEN INTENDED FOR ANOTHER ACFT. SUPPLEMENTAL INFO FROM ACN 572120: AS WE CHKED ON WITH ZDC; OUR XMISSION AND CTR'S WERE BLOCKED. AFTER THE SECOND XMISSION; WE HEARD A SOMEWHAT URGENT REQUEST FOR A DSCNT TO 11000 FT FOR A GARBLED CALL SIGN THAT ENDED WITH 'CD' (OURS WAS ABCD). IF WE HAD ACCEPTED THE WRONG CLRNC IT MAY HAVE BEEN BECAUSE OF THE STEPPED ON/GARBLED XMISSION OR THE FACT OF SIMILAR CALL SIGNS.