UNAUTH TKOF. PLT ACCEPTS ANOTHER ACFT'S CLRNC AND TAKES OFF.

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AFTER REPEATING MY IFR CLRNC (I ROUTINELY FILE IFR); UPON RECEIVING PERMISSION TO TAXI TO INTXN M; I CAUTIONED THE GND CTLR TO KEEP AN EYE ON US; INASMUCH AS WE WERE FIRST TIME STRANGERS. I BELIEVE I SAW ANOTHER SMALL ACFT PRECEDE ME TO INTXN M; WHICH HELPED GIVE ME A SUBCONSCIOUS IMPRESSION THAT THE AIRLINER LOCATED AT THE EXTREME END OF RWY 35R WAS PARKED; WHICH TO MY MIND EXPLAINED TO ME WHY I WAS GIVEN AN INTXN POS FOR TKOF; WHICH I DID NOT REQUEST. AFTER RUNUP; I ADVISED THE TWR CTLR THAT I WAS READY FOR TKOF. SHE TOLD ME TO HOLD SHORT. MY ACFT HAD NOT MOVED SINCE I PARKED FOR THE RUNUP. I CONTINUED TO HOLD UNTIL I HEARD AN INSTRUCTION '???? CLRED FOR TKOF WITHOUT DELAY.' I ACTUALLY DID NOT HEAR THE CALL SIGN CLRLY; HOWEVER; IT IS NOT USUAL IN MY EXPERIENCE TO HEAR A CTLR TELL AN AIRLINER TO TKOF WITHOUT DELAY; SO I ASSUMED THE DIRECTIVE WAS FOR ME. I REPLIED; 'XXXX IS ROLLING;' WHICH I ALWAYS SAY AT THIS TIME. THERE WAS NO REPLY FROM THAT COM. I IMMEDIATELY ROLLED INTO POS OVER THE SHORT DISTANCE AND PROMPTLY TOOK OFF. I WAS ABOUT 400 FT AIRBORNE WHEN THE LADY CTLR ADVISED ME THAT THE INSTRUCTION WAS FOR ANOTHER ACFT -- THE AIRLINER. I; OF COURSE; WAS MORTIFIED AND SURPRISED; YET IMMEDIATELY APOLOGIZED; EXPLAINING THAT I THOUGHT THE INSTRUCTION WAS FOR ME; AND VOICED MY SERIOUS CONCERN. THE CABIN LOUDSPEAKER IS ON THE CEILING POSITIONED SLIGHTLY IN FAVOR OF THE COPLT SEAT WHERE MY SISTER WAS SITTING. SHE ALSO DID NOT HEAR ANY COMS OTHER THAN OF THOSE DESCRIBED ABOVE.