G2 FLT CREW WITH ZTL AT FL410 MISTAKENLY ACCEPTS DSCNT CLRNC FOR SIMILAR SOUNDING ACFT.

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WHILE AT CRUISE FLT; FL410; WE WERE HANDED OFF TO ANOTHER ZTL FREQ. SHORTLY AFTER TUNING IN; WE BELIEVED WE WERE GIVEN A DSCNT CLRNC TO FL310. I THOUGHT THIS WAS UNUSUAL AS WE WERE STILL 90 MINS FROM OUR DEST. I ASKED THE REASON FOR DSCNT CLRNC AND WAS TOLD IT WAS FOR TFC. THE MOA'S OFF THE EAST COAST WERE IN EFFECT SO THERE WERE A LOT OF ACFT USING OVER LAND INSTEAD OF ATLANTIC RTES. I STARTED A DSCNT AND HAD THE FO CALL AGAIN TO VERIFY. THE CTLR SAID THAT CLRNC WAS NOT FOR US (ACFT ABC) BUT FOR 'ACR ABC.' WE BEGAN TO CLB FROM FL385 BACK TO FL410. WE STATED OUR POS AND ALT AND WERE HANDED OFF TO ANOTHER ZTL FREQ. SIMILAR CALL SIGNS CAN LEAD TO PROBS. I SHOULD HAVE BEEN MORE DIRECT IN MY QUESTIONING THIS CLRNC. THE CTLR SHOULD HAVE NOTICED THAT 2 READBACKS WERE FROM AN INCORRECT CALL SIGN. MY HOPE IS THAT AS THE VOICE FREQS BECOME MORE CONGESTED; AND MORE ACFT HAVE CALL SIGNS EASILY CONFUSED; WE WILL DEVELOP ELECTRONIC DATA DELIVERY OF AIRBORNE CLRNCS. WE ALREADY HAVE PDC'S THROUGH AFIS AND ACARS. THIS SHOULD NOT BE THAT COSTLY TO DEVELOP AND IMPLEMENT. UNTIL THEN; I KNOW I'LL TRY TO BE MORE CAREFUL OF CONFUSING CALL SIGNS.