FLC LANDED WITHOUT CLRNC AT IAH.

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ON OUR ARR INTO IAH ON FLT ABC; WE WERE TOLD TO CONTACT HOUSTON TWR ON FREQ 135.15. WHEN WE CONTACTED THE TWR; MY FO AND I HEARD ACR BCD CLRED TO LAND RWY 27. MY FO READ THE CLRNC TO LAND BACK. ON LOW APCH WE NOTICED A GREEN LIGHT SIGNAL FROM THE TWR. AFTER WE LANDED IN IAH; WE WERE TOLD TO CONTACT GND CTL. AFTER WE CONTACTED GND; WE WERE THEN TOLD TO CONTACT OUR COMPANY RAMP FREQ. RAMP ADVISED US THAT WE NEEDED TO CALL THE TWR. TWR TOLD US THAT THEY HAD BEEN CALLING US NUMEROUS TIMES ON FINAL AND DID NOT HEAR A RESPONSE. THEY ASKED US IF WE HAD RECEIVED A LNDG CLRNC. WE TOLD THEM THAT WE HAD; AND THAT WE ALSO SAW THE LIGHT GUN SIGNAL. AS A MEMORY AID; MY FO AND I LEAVE THE TAXI LIGHT OFF UNTIL WE HEAR OUR LNDG CLRNC. ON THIS OCCURRENCE; WE BOTH REACHED T TURN THE TAXI LIGHT ON WHEN WE HEARD OUR CLRNC. OUR RADIO FUNCTIONED PROPERLY BEFORE AND AFTER THE OCCURRENCE. I DO NOT KNOW IF SOMEONE ELSE GAVE US A CLRNC OR IF THE CTL TWR WAS NOT XMITTING ON THE CORRECT FREQ OR IF WE DID NOT HEAR THEIR NUMEROUS CALLS. I TALKED WITH THE TWR ON THE TELEPHONE; AND HE ADVISED US THAT THERE WAS NO PROB AND THANKED US FOR CALLING.