CREW CONCERNED THAT THEY FLEW AN APCH TO IAH THAT WAS NOT AUTH BY THEIR COMPANY. THIS FACT WAS LISTED IN COMPANY INFO THAT WAS AVAILABLE.

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AT APPROX IAH 328 DEG RADIAL 25 DME AND AT ABOUT 5200 FT MSL (DSNDING TO 3000 FT MSL) WE HAD RWY 15L AND VASI IN SIGHT. WE WERE ON THE RWY 15L LOC LINED UP WITH RWY 15L VISUALLY. AT 5200 FT MSL I DISCONNECTED THE GFMS AND AUTOPLT. MOMENTS LATER; WE WERE CLRED TO 2000 FT AND THE ILS TO RWY 15L. I MONITORED THE RWY 15L ILS COURSE AND GS AND FLEW VISUALLY TO RWY 15L. I BELIEVE WE DID NOT CALL THE RWY VISUAL (IN SIGHT) OR GET A VISUAL APCH TO RWY 15L. AFTER LNDG DUE TO LINGERING QUESTIONS ABOUT THE COMPANY MESSAGES ON OUR FLT PLAN; WE CONFIRMED COMPANY MESSAGE 'ILS RWY 15L; PROC NOT AUTH' AND 'NO REASON GIVEN FOR THIS CHANGE' MESSAGES ON OUR FLT PAPERWORK. WHEN I READ THE MESSAGE BEFORE FLT; I THOUGHT I READ RWY 15R INSTEAD OF RWY 15L ON THE MESSAGE (THERE ARE NORMALLY RESTRS TO RWY 15R IN THE MESSAGE). DUE TO THE BAD WX (WE HAD JUST STOPPED DEVIATING DUE TO TSTMS ABOUT 60 NM FROM IAH) AND THE SHORT FLT FROM DFW TO IAH; WE WERE VERY BUSY AND I DID NOT RECHK THE MESSAGES AS I NORMALLY DO BEFORE APCH. IN THE FUTURE; I WILL RECHK (AND HAVE THE FO CONFIRM) THE ARPT MESSAGES AND NOTAMS PRIOR TO APCH.