B767 FLC AFTER DEPARTING MCO LEARN THE CLRNC WAS FOR ANOTHER ACFT WITH A SIMILAR ACFT NUMBER ON A DIFFERENT FREQ.

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DEPARTING MCO AT XA49. CLRED INTO POS AND HOLD ON RWY 18L; TWR FREQ 124.3. CLRED FOR TKOF ON A 220 DEG HDG. FO READ BACK TKOF CLRNC AND CAPT DIALED HDG INTO MCP. AFTER DEP; DEP CTL ADVISED THE 'TWR SAID EVERYTHING KOSHER -- NO PROBS.' WE DID NOT UNDERSTAND COMMENT AND QUERIED DEP AND WERE ADVISED TO CALL NUMBER. UPON ARR IN ORD; CALLED AND WERE TOLD THAT TWR HAD CLRED ANOTHER FLT FOR TKOF ON RWY 17 AND THAT BOTH THE OTHER ACFT AND OUR FLT READ BACK THE TKOF CLRNC. TWR WAS XMITTING ON BOTH FREQS AND WE EVIDENTLY CONFUSED THE FLT NUMBER AND ACCEPTED THE CLRNC. TWR DID NOT ASK US TO ABORT THE TKOF NOR ADVISE THAT WE HAD ERRED. WE NEVER KNEW WE ACCEPTED THE WRONG TKOF CLRNC UNTIL ON THE GND IN ORD. TWR SHOULD NOT BE XMITTING ON 2 FREQS; AS THIS WAS THE PRIMARY CAUSE OF THE CONFUSION. FURTHER; IF TWR RECOGNIZED WE WERE DEPARTING IN ERROR; THEY SHOULD HAVE HAD US ABORT OUR TKOF SINCE THE VISIBILITY WAS EXCELLENT. THE FO AND I SPOKE WITH THE SUPVR OF BOTH DEP CTL AND THE TWR AT THE TIME OF OUR CALL. THE TWR SUPVR WHO WAS ON DUTY WHEN THE INCIDENT OCCURRED WAS NO LONGER ON DUTY. SUPPLEMENTAL INFO FROM ACN 563446: AFTER TAXIING INTO POS AND HOLD ON RWY 18L IN MCO; I RESPONDED TO WHAT I THOUGHT WAS OUR TKOF CLRNC WITH A HDG OF 200 DEGS. TKOF WAS NORMAL AND DEP WAS NORMAL. WHEN DEP CTL SWITCHED US TO CTR HE MADE A COMMENT REFING 'EVERYTHING IS OK WITH THE TWR.' WE QUERIED HIM ABOUT THIS AND RECEIVED A PHONE NUMBER FOR MCO TWR. AFTER ARR IN ORD; CAPT AND I CALLED THE MCO TWR. WE SPOKE WITH MR X AT XD32. HE STATED THAT WE TOOK AND READ BACK THE TKOF CLRNC FOR ANOTHER FLT WHO WAS IN POS ON RWY 17; AND THAT WE WERE NOT CLRED FOR TKOF. THE GND AND TWR FREQS IN MCO ARE SPILT E AND W. THE TWR CTLR WAS LISTENING TO EACH FREQ SEPARATELY AND XMITTING ON BOTH. WE COULD NOT HEAR ACFT ON THE E RWY. THE TWR CTLR ISSUED A TKOF CLRNC TO WHAT I THOUGHT WAS US. I READ BACK THE TKOF CLRNC AND THE CTLR DID NOT RESPOND WITH 'NEGATIVE; THAT WAS FOR ANOTHER ACFT' OR ANYTHING LIKE THAT. WE TOOK OFF AND HAD NO IDEA OF ANY PROBS UNTIL REACHING ORD AND TALKING WITH MR X; AND MR X DID SAY THAT THE TWR TAPES HAD BOTH ACFT RESPONDING TO THE CTLR'S TKOF CLRNC. WE DID NOT EVEN KNOW THERE WAS ANOTHER ACFT IN POS AND HOLD AT MCO OR WHY THE TWR CTLR DID NOT ABORT US.