A C152 PVT PLT MAKES TOO EARLY A TURN AT 450 FT WHEN DEP RWY 9R AT FLL; FL.

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I WAS GIVEN TKOF CLRNC FOR RWY 9R AT FLL ARPT. I WAS SQUAWKING 1200 FOR A VFR FLT TO NORTH PERRY ARPT; APPROX 8 MI TO THE SW. I TOOK OFF AND CLBED UNTIL I WAS OVER THE DEP END OF THE RWY; HDG E; THEN STARTED A R TURN WHILE CLBING TO THE S; THEN SW TOWARD NORTH PERRY ARPT. A FEW SECONDS AFTER I STARTED THE R TURN; THE FLL TWR CTLR SAID; 'RADAR CONTACT; WHAT IS YOUR ALT?' I LOOKED AT MY ALTIMETER AND REPLIED '450 FT.' THE TWR DID NOT SAY ANYTHING FURTHER. I THEN ASKED FOR A FREQ CHANGE TO NORTH PERRY TWR; WHICH WAS GRANTED. I THEN STARTED WONDERING WHY THE CTLR HAD ASKED FOR MY ALT. HAD I MISSED A CALL REQUESTING ME TO FLY E ON THE RWY HDG UP TO A CERTAIN ALT BEFORE MAKING THE TURN? OR HAD I BEEN ASKED TO WAIT FOR TWR APPROVAL BEFORE MAKING THE TURN? OR HAD I TURNED OUT AT TOO LOW AN ALT? I HAD FLOWN THIS FLT PATH ON NUMEROUS OCCASIONS AND HAD ALWAYS BEEN ALLOWED TO MAKE AN IMMEDIATE R TURN TO THE SW; SO THAT IS WHAT I WAS EXPECTING AND THAT IS WHAT I DID. IF I WAS TOLD TO DO OTHERWISE; MY MIND DID NOT HEAR IT UNDER THE ASSUMPTION THAT THE ROUTING WOULD BE THE SAME AS ON PREVIOUS OCCASIONS. WHAT I SHOULD HAVE DONE -- AND WHAT I WILL DO IN THE FUTURE -- IS TO VERBALLY REQUEST AN IMMEDIATE TURNOUT AND VERIFY THE REPLY I GET FROM THE TWR CTLR. THE CTLR NEVER ASKED ME TO CALL THE TWR VIA PHONE; NOR DID THE CTLR EVER SAY ANYTHING REGARDING THE ALT; SO I'M NOT EVEN SURE IF I MADE A MISTAKE; BUT I DID LEARN A VALUABLE LESSON. ALWAYS GET VERBAL CONFIRMATION RATHER THAN ASSUME WHAT I THINK TO BE TRUE.