B737 LNDG ATL ACCEPTS DSCNT CLRNC ISSUED TO SIMILAR CALL SIGN ACFT.

Narrative

WHILE DSNDING INTO THE ATL AREA; WE WERE ACFT ABCC. ACFT ADCC WAS ALREADY ON THE FREQ. WE STARTED TO EXERCISE VIGILANCE AND NOT TAKE THE WRONG INSTRUCTIONS FROM THE CTLR. I HAD MISTAKENLY READ BACK MY CALL SIGN AS ADCC; BUT IMMEDIATELY CORRECTED MYSELF IN THE SAME XMISSION. WE RECEIVED A CLRNC TO 9000 FT AND RESPONDED WITH OUR CALL SIGN 'ABCC LEAVING 11000 FT.' THE CTLR SAID 'ABCC; MAINTAIN 11000 FT.' WE HAD REACHED 10600 FT BEFORE WE RETURNED TO 11000 FT. IT IS UNCLR WHETHER WE RECEIVED THE WRONG CLRNC OR THE CTLR GAVE US THE WRONG CLRNC; OR THE RIGHT CLRNC WAS GIVEN AND THE CTLR JUST DECIDED TO STOP US AT 11000 FT. WE RECEIVED THE CLRNC FOR THE OTHER ACFT AND THE CTLR DID NOT CATCH US ON THE READBACK. THE ACFT REACHED 10600 FT AND RETURNED TO 11000 FT. NO CONFLICT WAS NOTED. NOTHING FURTHER WAS SAID BY THIS OR SUBSEQUENT CTLRS. THIS PROB; IF THERE WAS ONE; WAS BROUGHT ON BY THE SIMILAR CALL SIGNS. THE ATL AREA WAS VERY BUSY AND THE CTLR WAS VERY BUSY AS WERE WE. WE HAD MADE A CONSCIOUS ATTEMPT TO LISTEN FOR THE OTHER CALL SIGN AND NOT TO MAKE A MISTAKE. IN THAT TYPE OF ENVIRONMENT; ONE CAN'T BE TOO CAREFUL.