A320 DEP FROM MCO FAILED TO CANCEL TKOF AS INSTRUCTED BY ATC BECAUSE OF UNCERTAINTY AS TO ATC INTENTIONS.

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AFTER BEING CLRED 'POS AND HOLD' ON RWY 18L; AN ACFT CLRING RWY 18R WAS TOLD TO HOLD SHORT OF RWY 18L. HE DID NOT GIVE THE CORRECT RESPONSE TO THE TWR AND THERE WERE 3-4 RADIO XMISSIONS BTWN THEM. PRIOR TO THIS; WE HAD BEEN CLRED FOR TKOF ON RWY 18L. THE FO HAD CALLED '80 KTS' AND WE BOTH HEARD A 'TKOF CLRNC CANCELED' RADIO CALL BUT HEARD NO CALL SIGN WITH IT. (THE TWR WAS CTLING BOTH SIDES OF THE ARPT USING SEPARATE FREQS). I WAS WATCHING THE AIRPLANE TO MAKE SURE HE WAS INDEED HOLDING SHORT OF OUR RWY AND MADE A COMMENT TO THAT EFFECT. AFTER TKOF; THE TWR CALLED US FOR A RADIO CHK AND TOLD US 'I HAD CANCELED YOUR TKOF CLRNC AND I WAS TRYING TO GET A HOLD OF YOU SEVERAL TIMES.' HE THEN SENT US TO DEP CTL WITHOUT FURTHER COMMENT. SUPPLEMENTAL INFO FROM ACN 680506: I DID HEAR SOMETIME DURING THE ROLL; AFTER 80 KTS; A CALL TO CANCEL TKOF CLRNC. I DID NOT HEAR OUR CALL SIGN. FRANKLY; I THINK I DISMISSED THIS BECAUSE I DID NOT HEAR OUR CALL SIGN OR THE TWR HAD NO URGENCY IN HIS VOICE AND WE WERE ALREADY GOING FAST ENOUGH THAT I WOULD EXPECT TO HEAR THE WORDS 'ABORT' OR 'REJECT.' A CALM VOICE SAYING; 'CANCEL TKOF CLRNC' JUST DOES NOT REGISTER; IN A HIGH SPD; HIGH NOISE ACFT. 'ABORT; ABORT' WOULD HAVE BEEN AN APPROPRIATE TWR CALL DURING THIS NOISY VERY BUSY TIME IN THE COCKPIT.