AN AIRBUS A320 FLC EXECUTED A MISSED APCH AT LAS WHEN THE LNDG CLRNC WAS FOR ANOTHER RWY.

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APPROX 30-35 MI FROM RWY 25L AT LAS; WE WERE CLRED FOR VISUAL APCH TO RWY 25L (WE WERE ON RWY 25L LOC) WHILE MAINT VISUAL CONTACT WITH COMPANY ACFT AHEAD OF US; ALSO TO MAINTAIN 210 KTS OR BETTER UNTIL 5 OR 10 MI FINAL (CAN'T REMEMBER WHICH) AS PER ATC INSTRUCTIONS. AS PF; I WAS ALREADY AT 250 KIAS AND MAINTAINING THIS UNTIL APPROX 10 MI FROM RWY. I THEN BEGAN SLOWING AS WE WERE BEGINNING TO CLOSE WITH COMPANY ACFT AHEAD OF US. I BELIEVE WE WERE AT APPROX 6-7 MI FROM RWY. APCH CTL HANDED US OFF TO LAS TWR. WE CONTACTED TWR AND WE WERE CLRED TO LAND ON RWY 19L. THIS IS WHERE THE CONFUSION STARTED; AS WE WERE TOO CLOSE TO RWY 25L THRESHOLD TO REALLY INITIATE A CIRCLE TO LAND MANEUVER AND AT THE SAME TIME I SPOOLED UP THE ENGS TO MAINTAIN PRESENT AIRSPD; ALT AND CONFIGN IN ANTICIPATION OF A CANCELED LNDG CLRNC ON RWY 25L; OR A GAR; ETC. WHILE RAPIDLY SORTING THIS OUT WITH THE TWR; WE CLOSED WITH PRECEDING TFC BECAUSE OF OUR STABILIZED AIRSPD (APPROX 160 KTS) UNTIL I DECIDED TO GO AROUND BECAUSE OF IMPENDING TFC CONFLICT. IN THE MEANTIME WE DETERMINED WE HAD INADVERTENTLY CONTACTED LAS TWR ON 118.75 WHICH WAS THE FREQ FOR THE RWY 19L/R COMPLEX INSTEAD OF THE CORRECT FREQ OF 119.9 FOR RWY 25L. I DON'T KNOW WHY THE TWR RESPONDED WITH OUR CORRECT CALL SIGN AND CLRED US TO LAND ON RWY 19L -- THERE MUST HAVE BEEN SOME CONFUSION ON HIS PART AS WELL. AFTER DETERMINING OUR POS (CLOSE FINAL FOR RWY 25L) HE SENT US BACK TO THE CORRECT FREQ 119.0 (THAT'S WHEN WE REALIZED OUR ERROR). UPON SWITCHING TO 119.9 THE TWR WAS ALREADY ISSUING A GAR; WHICH WE WERE IN THE PROCESS OF COMPLETING. WE ULTIMATELY CLBED TO 5000 FT MSL RWY HDG AND WERE VECTORED TO A R DOWNWIND TO RWY 19R AND CLRED TO LAND RWY 19R. THIS WE COMPLETED WITHOUT FURTHER INCIDENT.