CTLR MIXING 2 RADIO CALL SIGNS FOR SAME COMPANY ACFT. FLC FOLLOWS DSCNT CLRNC INTENDED FOR PROCEEDING ACFT.

Narrative

LOCATION: HOBEE 360 DEG RADIAL; 120 DME. WE (TRIP 1) HAD BEEN FOLLOWING TRIP 2 APPROX 40 NM IN TRAIL FOR OUR ENTIRE ENRTE PORTION OF JFK-MIA. AT APPROX 120 NM N OF HOBEE; PROCEEDING DIRECT TO HOBEE; ZJX CLRED US (TRIP 1) TO DSND TO FL280; TO WHICH WE ACKNOWLEDGED. TCASII SHOWED AN ACFT BELOW US AT FL290 HDG THE OPPOSITE DIRECTION. ALTHOUGH THAT ACFT WAS OFF OF OUR L WING AT THE 5 MI RADIUS ON TCASII; WE LET HIM PASS BEFORE INITIATING OUR DSCNT. LESS THAN 1 MIN LATER; ZJX AGAIN CLRED US TO FL280; TO WHICH WE RESPONDED 'WE ARE PASSING FL300 FOR FL280.' THE CTLR ANSWERED THAT THE PREVIOUS CLRNC WAS FOR TRIP 2 AND NOT TRIP 1; BUT AS LONG AS WE WERE DSNDING TO CONTINUE DOWN TO FL280. UPON HEARING THIS; THE OTHER ACFT INFORMED ZJX THAT THEY HAD NEVER BEEN GIVEN FL280 AND THAT CTLRS HAD BEEN MIXING US UP ALL NIGHT. ATC THEN CLRED TRIP 2 TO DSND FROM FL310 TO FL280. THIS ENDED THE EVENT. SCHEDULING SUCH SIMILAR CALL SIGNS ON THE SAME RTE AT THE SAME TIME CAN ONLY LEAD TO THIS TYPE OF CONFUSION.