RESPONSE TO WRONG CALL SIGN AND LATER PROBS WITH CLRNC INTERP LEAD TO ALTDEV ALT OVERSHOT EXCURSION AND HDG TRACK DEVS. RPR CITES INTENTIONAL SLURRING OF ACFT CALL SIGNS THAT WERE DIRECTED TO ONE PARTICULAR AIRLINE.

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ON DEP; THE NARITA DEP CTLR ON 124.2 REFUSED TO USE CLR CALL SIGNS. ONE OF OUR FLTS WAS CALLED 'NOSUESIX;' AND WE WERE CALLED 'NOSEUESTUH.' ANOTHER INDECIPHERABLE CALL SIGN WAS ADDRESSED TO ANOTHER ONE OF OUR FLTS. THUS; IT BECAME NECESSARY TO REQUEST DIRECTIONS (VECTORS AND ALTS) TO BE REPEATED 2; 3; EVEN 4 TIMES. (I HAVE FLOWN REGULARLY IN AND OUT OF JAPAN SINCE 1962; AND CAN SPEAK JAPANESE FAIRLY WELL; AS WELL AS UNDERSTAND JAPANESE ACCENTED ENGLISH.) IN ONE CASE; WE ACCEPTED AND READ BACK A RADAR VECTOR AND ALT ASSIGNMENT MEANT FOR SOMEONE ELSE. WE ASKED THE CTLR SPECIFICALLY IF THIS WAS MEANT FOR US; AND HE GAVE AN UNINTELLIGIBLE REPLY. WE FOLLOWED THE CLRNC (A L TURN TO 090 DEGS; CLB TO 11000 FT) AND WERE SUBSEQUENTLY GIVEN A R TURN TO 180 DEGS AND 9000 FT ALT ASSIGNMENT. AT ONE POINT; I DIRECTLY ASKED THE CTLR TO BE MORE CLR IN USING THE AIRLINE NAME AND FLT NUMBER. HE WOULD NOT DO SO; DESPITE MY CALL. HIS UNINTELLIGIBLE REPLY SOUNDED LIKE A REFUSAL TO DO SO. HIS CALLS TO COMPETITOR FLTS WERE CLR. I BELIEVE THAT HE INTENTIONALLY SLURRED OUR FLT NUMBER CALLS FOR ARCANE REASONS OF HIS OWN. THIS INCIDENT CALLS INTO QUESTION THE PRACTICES AND TRAINING OF JAPAN ATC. I QUESTION WHETHER SOME PERSONNEL SHOULD BE WORKING IN SUCH AN ENVIRONMENT.