IFR C414 AT PVW DEPARTED WITHOUT ATC RELEASE.

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AFTER PAX LOADING AND ENG START; I CONTACTED PVW CLRNC ON 121.7 AND ADVISED THEM I WOULD DEPART PVW RWY 22 AND WOULD BE READY IN A COUPLE OF MINS. I RECEIVED THE CLRNC; HEARD THE WORD 'RELEASED;' READ THE CLRNC BACK WITH A THANK YOU AND DEPARTED PVW RWY 22 AND CONTACTED LBB APCH ON 119.2. ABOUT 10 MINS INTO THE FLT; LBB APCH ASKED ME TO CALL THEM. I ASKED WHY AND WAS TOLD I DEPARTED WITHOUT A RELEASE. AS STATED BEFORE; I HEARD THE WORD 'RELEASE' IN THE CLRNC. AGAIN THE WX WAS VFR; SO I DIDN'T UNDERSTAND THE REASON FOR THE CALL. ARRIVING ERV; I DID CALL LBB TWR AND WAS PUT THROUGH TO A SUPVR. HE ASKED ABOUT THE WX IN PVW; I TOLD HIM I DEPARTED VFR AND TOLD HIM I HEARD THE WORD 'RELEASE' IN THE CLRNC. I THEN WAS TOLD AFTER HE LISTENED TO THE TAPES THAT INDEED; I DID HEAR THE WORD 'RELEASE' AND HE KNEW I THOUGHT I WAS RELEASED. HE THEN INFORMED ME THAT HE TALKED WITH THE CTLR AND WHEN I READ BACK THE CLRNC WITHOUT ANY MENTION OF A RELEASE TIME THAT THE CTLR SHOULD HAVE VERIFIED WITH ME THAT THERE WAS A RELEASE AND A VOID TIME WHICH I DID NOT HEAR. THERE HAVE BEEN PROBS WITH THE PVW CLRNC FREQ IN THE PAST NOT WORKING PROPERLY. I BELIEVE NO FAR'S WERE BROKEN IN ANYWAY.