ACFT EXCURSION FROM ASSIGNED ALT ON LAX CIVET PROFILE.

Narrative

CLRED FOR REEDR 2 ARR AFTER HEC WHILE FLYING IN AN LGT. SUBSEQUENTLY CLRED BY NEXT CTLR; 'AFTER HEC; DIRECT CIVET; DIRECT LAX.' APCHING CIVET; CLRED BY CENTER CTLR TO FLY CIVET 2 PROFILE DSCNT. JUST OUTSIDE ARNES SENT OVER TO APCH CTL AND RPTED LEVEL 10000; WITH ATIS 'X'. GIVEN CLRNC TO TURN R 10 DEG; MAINTAIN 10000 TO INTERCEPT 24R LOC FREQ 108.5 AND ATIS 'Y' NOW CURRENT. TOLD CAPT I'D BE OFF FREQ FOR A MIN TO GET NEW ATIS. WHILE LISTENING TO NEW ATIS; NOTICED ACFT DSNDING OUT OF 10000 AND ASKED IF WE HAD BEEN CLRED OUT OF 10000. CAPT HAD MISUNDERSTOOD CLRNC AND THOUGHT THAT WE WERE STILL CLRED FOR THE PROFILE DSCNT. REVERSED DSCNT AT 9500 FT. SUBSEQUENTLY CLRED TO 8000 WHILE CLBING BACK TO 10000. FREQ CONGESTION WOULD NOT ALLOW US TO QUESTION OUR CLRNC. ELECTRIC JETS ARE TOO HARD TO DEPROGRAM ONCE VNAV IS IN CTL. A MOMENTARY DISTR WITH VNAV PROGRAMMED ALLOWS ACFT TO DSND BEFORE YOU ARE READY. EVEN DISENGAGING AUTOPLT ONCE ACFT HAS INITIATED DSCNT MAKES IT VERY DIFFICULT TO REMAIN WITHIN 300 FT OF ASSIGNED ALT. I HAD TO RPT TO NATIONAL GUARD DUTY AT A REMOTE STATION FOR 4 DAYS AFTER MY AIRLINE TRIP. I MAILED THIS RPT AS SOON AS POSSIBLE.