MULTIPLE RWY OP ACR X HAD LTSS FROM ACR Y ON PARALLEL RWY. SYS ERROR.

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ACR X WAS ON APCH CTL VECTOR FROM ATL APCH CTL ON AN ASSIGNED HDG FOR DOWNWIND LEG FOR VISUAL APCH TO RWY 26R ILS. APCH CTLR GAVE US 2 TA'S ON A CESSNA ACFT WHICH HE WAS NOT IN CONTACT WITH WHICH HE WAS OBVIOUSLY CONCERNED WITH. WE RPTED A VISUAL ON CESSNA AFTER FIRST ATL ALERT; THEN RECEIVED A SECOND ALERT AS WE WERE CONVERGING ON THE INBOUND COURSE TO RWY 26R AND 26L AND RWY 27. WE WERE NOT GIVEN A TURN OR ADVISORY THAT WE WERE BEING FLOWN OR VECTORED THROUGH THE LOC -- TOO LATE FOR A L TURN! DUE TO VISUAL ON OTHER TFC; AND WITH A TA AND LATER CLB TCASII ALERT FOLLOWED BY TURN R INSTRUCTION I WAS IN A CLB AND ROLLED ACFT TO APPROX 60 DEGS R BANK CLBING TURN FLYING BEHIND AND ABOVE A B757 BELOW AND INBOUND TO RWY 27 AT ATL. LANDED ACFT AFTER BEING CHANGED TO TWR AND APPROX 180 DEGS OF TURN BACK TO INBOUND COURSE FOR APCH TO RWY 26R; ON RWY 26L PER TWR CLRNC TO LAND. ON GND; I TELEPHONED ATL APCH CTL AND SPOKE TO SUPVR AND APCH CTLR WHO APOLOGIZED FOR HIS ERROR IN NOT GIVING OR CHANGING OUR HDG FOR IMPROPER TURN TO FINAL APCH; AND ADMITTING HIS MISTAKE.