ACR-MLG ALT DEVIATION IN RESPONSE TO WRONG CALL SIGN AND CLOSE PROX WITH SAME DIR TRAFFIC A GA-SMT.

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ASSIGNED 17000' BY ZLA AND WAS ON A VECTOR TOWARD SANTA CATALINA VOR; WITH A CRUISE SPD OF 305 KIAS. INITIALLY WE WERE ASKED TO SLOW TO 280 KTS AND DSND TO 1000'. AT ABOUT 16000' WE WERE CLRED TO 14000' AND ASKED TO SLOW TO 250 KTS. AT ABOUT 14000' WE WERE CLRED TO 11000'. DURING THE PROCESS OF LEVELING AT 11000'; A CLRNC WAS RECEIVED TO DSND TO 5000'; EXPEDITING THROUGH 6000'; AND TO RESUME NORMAL AIRSPD. THE CLRNC WAS ACKNOWLEDGED XOE TO DSND TO 5000'; EXPEDITING THROUGH 6000'. ONE TFC ADVISORY WAS GIVEN BY ZLA WHEN WE WERE DSNDING THROUGH ABOUT 10000'; THAT THEY HAD A TARGET AT OUR 12 O'CLOCK AND 8 MI. AS WE WERE DSNDING THROUGH ABOUT 8700'; AN ACFT WAS OBSERVED AHEAD AT ABOUT THE 12 O'CLOCK POS; A LITTLE LOW AND APPROX 1 MI AHEAD. INITIALLY IT APPEARED THAT THE TARGET WAS ABOUT 7500'. OUT ACR WAS LEVELED OFF AT 8500' UNTIL WE WERE CLR. A COMMENT WAS MADE TO ZLA BY THE LIGHT TWIN THAT AN ACFT HAD PASSED RIGHT OVER THEM. ZLA THEN INQUIRED ABOUT XOE ALT AND WAS TOLD 8500' DSNDING TO 5000'. THE CENTER THEN REPLIED THAT THE CLRNC WAS FOR DGOE NOT XOE. RIGHT AFTER CHKING IN ON THE EFFECTED SECTOR FREQ ONE CALL TO DGOE WAS MADE; BUT NEITHER THE F/O NOR I HEARD ANY ADDITIONAL CALLS TO DGOA AFTER THAT. THE WX AT THE TIME OF THE INCIDENT WAS A SOLID CLOUD LAYER; WITH THE TOPS SOMEWHERE AROUND 4000'. WE WERE FLYING INTO A VERY BRIGHT SUN WHICH WAS ALSO REFLECTING OFF THE CLOUDS; AND EFFECTIVELY REDUCING OUR FORWARD VIS. ONE THING I DO NOT UNDERSTAND IS WHY ZLA DID NOT NOTICE OUR ALT DEVIATION WHEN WE CONTINUED OUR DSCNT FROM AN ASSIGNED ALT OF 11000 TO 5000'. I DID PERSONALLY QUESTION WHY THE CENTER WOULD TELL US TO RETURN TO NORMAL SPD WHEN WE WOULD HAVE TO BE AT 250 KIAS BELOW 10000'; BUT BECAUSE OF THE AMOUNT OF RADIO TFC; I DID NOT THINK IT ADVISABLE TO ASK THEM. I ALSO DID NOT GET A POSITIVE RESPONSE FROM THE CENTER AFTER ACKNOWLEDGING OUR CLRNC; BUT SO OFTEN IN A HIGH DENSITY TFC AREA WITH A LOT OF RADIO XMISSIONS; A CLRNC IS GIVEN AND AN ACKNOWLEDGEMENT MADE W/O FURTHER COMS. AS IT TURNED OUT MY READBACK TO ZLA WAS BLOCKED BY ANOTHER XMISSION; AND CONSEQUENTLY THE CENTER NEVER REALIZED THAT BOTH XOE AND DGOE HAD READ BACK THE SAME CLRNC.