FLC OF ACR MLG ACFT DEVIATED FROM ASSIGNED APCH CLRNC DUE TO ATC CTLR CLRNC CONGESTION.

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INBOUND TO DFW ON BLUE RIDGE ARR RTE; WE WERE HANDED OFF TO DFW APCH CTL WHILE DSNDING TO 9000 FT. APCH CTL TOLD US (ACR #1) TO EXPECT VECTORS FOR AN ILS TO RWY 17L AND TO FLY HDG 245 DEGS; DSND TO 5000 FT. SHORTLY THEREAFTER; AN ACR #2 FLT CHKED ON THE FREQ AND WAS TOLD TO EXPECT AN ILS TO 17L AND CAUTION THAT ACR #3 WAS ON THE FREQ. SHORTLY THEREAFTER; WE WERE TOLD TO FLY HDG 250 DEGS AND TO EXPECT AN ILS TO RWY 18R AND CHANGE TO ANOTHER FREQ. UPON CHK IN; WE WERE AGAIN TOLD TO EXPECT ILS 18R AND TO DSND TO 3000 FT AND SLOW TO 180 KTS. THIS CTLR WAS HAVING DIFFICULTY COMMUNICATING WITH AN ACR #1 FLT BEING VECTORED TO AN ILS 17L. THE CTLR THEN SAID 'ACR #1; CROSS YOHAN INTXN AT OR ABOVE 3000 FT; CLRED FOR ILS 17L APCH.' WE THOUGHT THIS WAS ODD; SO THE CAPT TRIED TO VERIFY THIS BY READING BACK THE CLRNC. THE CTLR FAILED TO ANSWER US; POSSIBLY DUE TO A BLOCKED XMISSION FROM ANOTHER ACFT. SUBSEQUENT ATTEMPTS BY MY CAPT TO VERIFY THE CLRNC ALSO WENT UNANSWERED. SINCE I HAD HEARD CLRED ILS 17L; I TUNED IN THE LOC FOR 17L AND NOTICING THAT WE WERE PAST (TO THE W OF) IT; I TURNED BACK TO APPROX 150 DEGS TO ESTABLISH AN INTERCEPT HDG FOR 17L. ON 1 ATTEMPT TO VERIFY; THE CAPT ASKED IF ACR #1 IS CLRED FOR ILS 17L AND THE RESPONSE WAS 'AFFIRMATIVE;' (NO CALL SIGN VERBALIZED) SO THE CAPT ASKED AGAIN; 'WHO IS CLRED FOR ILS 17L' AND NO ANSWER! AFTER SEVERAL ANXIOUS MOMENTS; AND MORE ATTEMPTS AT VERIFYING OUR ASSIGNED RWY; ANOTHER CTLR'S VOICE CAME ON (POSSIBLY A SUPVR) AND SAID; 'ACR #1; TURN R TO 210 DEGS AND INTERCEPT THE LOC FOR 18R.' I THEN TURNED TO 210 DEGS AND TUNED IN THE LOC FREQ FOR 18R; BUT FAILED TO ARM THE LOC CAPTURE MODE OF THE AUTOPLT; SINCE BY NOW I WAS GETTING A LITTLE RATTLED. AS I WATCHED THE LOC COURSE CTR AND START TO DRIFT OFF THE L WITHOUT CAPTURING; I MANUALLY TURNED TO INTERCEPT IT AND THEN ARMED THE CAPTURE MODE. THE NEW CTLR'S VOICE THEN SAID; CALMLY; 'ACR #1; FLY HDG 160 DEGS; CROSS THE MARKER AT OR ABOVE 2300 FT; CLRED ILS 18R APCH; MAINTAIN 170 KTS TO THE MARKER.' AN UNEVENTFUL ILS 18R APCH AND LNDG WAS THEN ACCOMPLISHED. I BELIEVE THIS INCIDENT WAS CAUSED BY THE CTLR'S FAILURE TO LISTEN TO OUR READBACK AND THE ISSUANCE OF A CLRNC TO US THAT WAS MEANT FOR ANOTHER ACFT. IN MY 21 YRS OF FLYING; I HAVE NEVER HEARD SO MUCH CONFUSION ON APCH OR WAITED SO LONG FOR CONFIRMATION OF AN APCH CLRNC.