MLG FLC TOOK CLRNC OF ANOTHER FLT WITH SAME FLT NUMBER.

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WE WERE LEVEL AT 11000 FT ON THE GLAND ARR INTO IAH. I WAS THE FO ON THE FLT AND THE PF. THERE WAS A DSCNT CLRNC GIVEN TO MAINTAIN 6000 FT. THE CAPT ACKNOWLEDGED THE CLRNC WITH OUR CALL SIGN AND FLT NUMBER. AS WE PASSED THROUGH 10500 FT; THE CTLR SAID WE HAD TFC AT 1 O'CLOCK POS. WE RPTED THE TFC IN SIGHT AND WERE TOLD TO MAINTAIN VISUAL SEPARATION WITH THE TFC; WHICH WE ACKNOWLEDGED WE WOULD DO. THE CTLR THEN TOLD US TO MAINTAIN 11000 FT. WE IMMEDIATELY CLBED BACK TO 11000 FT. WE WERE THEN VECTORED FOR THE VISUAL APCH TO RWY 8 WITHOUT ANY FURTHER INCIDENTS. THE CTLR NEVER QUESTIONED US OR ASKED US TO CALL ANYONE. WE DID NOTICE AFTER THE INCIDENT THAT THERE WAS ANOTHER AIRLINE IN THE VICINITY WITH THE SAME FLT NUMBER. IF INDEED THIS DSCNT CLRNC WAS MEANT FOR THE OTHER ACFT; WE COULD PROBABLY HAVE AVOIDED THIS INCIDENT IF THE CTLR HAD WARNED US ABOUT THE 2 FLT'S FLT NUMBERS BEING THE SAME. BOTH THE CAPT AND MYSELF DISCUSSED THE INCIDENT AND WE BOTH WERE POSITIVE THAT WE HEARD THE CLRNC TO DSND GIVEN TO OUR FLT NUMBER. SINCE THE CTLR NEVER QUESTIONED US OR TOLD US TO CALL HIM ON THE GND; WE THOUGHT IT MIGHT HAVE BEEN AN ERROR ON HIS SIDE.