DC9 FLC GIVES ZME 2 OPPORTUNITIES TO CORRECT AND CLARIFY READBACK PRIOR TO DSCNT. AFTER OTHER SIMILAR COMPANY QUESTIONS ZME; ZME RECOGNIZES AND CORRECTS CLRNC INTENT.

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JUST STARTING THE UJM MARVELL STAR FOR MEM; WE WERE LEVEL AT FL230. THE CTLR MADE A XMISSION 'ACR XX_ (UNKEYED) DSND AND MAINTAIN 17000 FT.' WE WERE ACR XXB AND THERE WAS AN ACR XXA ALSO ON THIS SECTOR FREQ. SO TO TRY TO ASCERTAIN WHICH ACFT THIS WAS FOR; I ASKED FOR THE CTLR TO 'SAY AGAIN.' AT THIS TIME; THE CTLR SAID 'ACR XX_ (UNKEYED PORTION) DSND AND MAINTAIN 17000 FT.' THIS TIME THE LAST DIGIT WAS ONLY CLIPPED FOR ABOUT 1/2 OF THE SYLLABLE. I THOUGHT I HEARD ENOUGH OF IT IN THE XMISSION TO ACCEPT THE CLRNC. TO MAKE SURE THAT THIS WAS FOR US; I PAUSED BEFORE READBACK TO SEE IF THE OTHER ACR ANSWERED THE CLRNC; JUST FOR ADDITIONAL CONFIRMATION. THEN TO STRESS FURTHER THAT THE CLRNC WAS FOR US (ACR XXB); I OVERLY ANNUNCIATED THE READBACK WITH VERY STRONG DICTION ON 'ACR XXB.' I THEN PAUSED AGAIN TO SEE IF THE CTLR CORRECTED THE READBACK. THERE WASN'T. SO; I DIALED IN 17000 FT IN THE ALT REMINDER AND THE FO STARTED THE ACFT DOWN. AFTER APPROX 20 SECONDS; IT MUST HAVE OCCURRED TO THE CREW OF ACR XXA THAT THEY WERE AT THE NORMAL PLACE IN THE ARR; THAT THEY SHOULD HAVE BEEN GIVEN LOWER; THAT THEY THEN SAID; 'WHAT DO YOU WANT ACR XXA TO DO?' THE CTLR THEN UNDERSTOOD WHAT HAPPENED AND REISSUED CORRECTIVE CLRNCS TO BOTH ACR XXA AND ACR XXB. THERE WAS NO OTHER CONFLICT WITH ANY OTHER ACFT. WE RETURNED TO FL230 FROM FL226. CAUSES ARE AS FOLLOWS: 1) MULTIPLE/SIMILAR CALL SIGNS OR FLT NUMBERS. 2) CTLR NOT LISTENING TO READBACKS. 3) CLIPPED XMISSIONS. 4) I TRULY THOUGHT I HAD DONE ALL THAT I COULD TO PREVENT THIS OCCURRENCE. 5) I SHOULD HAVE ASKED A 'THIRD' TIME OR UNTIL THE XMISSION WAS PERFECTLY CLR.