C402 CREW; IN DSCNT TO ACK; OVERSHOT THEIR ASSIGNED ALT; RESPONDING TO ANOTHER'S CLRNC.

Narrative

I WAS DSNDING ORIGINALLY OUT OF 7000 FT FOR 5000 FT ON A VECTOR FOR THE VISUAL 6 AT ACK. THE APCH FREQ WAS BUSY AS WELL AS OUR COMPANY FREQ AT THE TIME WHICH WE ARE REQUIRED TO MONITOR. I THOUGHT WHAT I HEARD WAS A HDOF FOR ME TO CALL ACK TWR. I ACKNOWLEDGED 'ACFT X TO NANTUCKET; ROGER' AND SWITCHED OVER TO ACK TWR. I CALLED THEM 20 NW; INBOUND WITH ATIS OUT OF 3700 FT FOR 3000 FT. THEY ASKED ME IF I WAS VFR OR IFR. I STATED 'I BELIEVE I WAS ON A HDOF; STILL ON AN IFR FLT PLAN.' THEY SAID NO I WAS NOT AND TO CALL CAPE APCH AGAIN. I CALLED BACK AGAIN; AND CAPE SAID I WAS NOT HANDED OFF AND SAID TO ME 'WELL; NOW YOU MIGHT AS WELL CONTINUE TO 3000 FT!' I SUDDENLY REALIZED I WAS NOT CLRED ORIGINALLY BELOW 5000 FT; BUT THOUGHT I HAD BEEN; ALONG WITH THE SUPPOSED HDOF TO THE TWR. NOW I WAS OUT OF 3300 FT FOR 3000 FT. ALL CONTINUED FINE AND I WAS HANDED OFF TO TWR. TWR CLRED ME FOR LNDG. UPON ARR; I WAS INSTRUCTED TO CALL CAPE APCH BY PHONE. I DID SO; AND SPOKE TO A NICE GUY THERE WHO RPTED HIMSELF AS THE SUPVR THERE (I DON'T RECALL HIS NAME). HE SAID TO ME THAT 'EVEN THOUGH IT'S NOT REALLY A BIG DEAL NOW;' HE WANTED ME TO BE AWARE OF WHAT I HAD DONE AND THAT COME THE BUSY SEASON; WE ALL NEED MORE OF A HEADS-UP AND LISTEN MORE CAREFULLY. HE KNOWS I RESPONDED ACCIDENTALLY FOR ANOTHER HDOF TO ACK TWR; BUT COULD NOT GET BACK TO ME BEFORE I SWITCHED OVER. ALSO; HE STATED HE HAD TO VECTOR A BE1900 TO A HDG OF 170 DEGS AS A RESULT OF MY DSCNT. HE WAS REASSURING THAT THIS WAS NOT AN INCIDENT TO WORRY ABOUT AND I ADMITTED MY ERROR IN THINKING I WAS CLRED FOR FURTHER DSCNT AND HDOF TO TWR.