ALTDEV ALT EXCURSION - THE CAPT REQUESTED A HIGHER ALT; BUT ARTCC REFUSED BECAUSE OF CONFLICTING TFC THEN THE FO CLBED ANYWAY.

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CAPT REQUESTED CLRNC FROM FL330 TO FL350 BECAUSE OF LIGHT TURB AT FL330. THIS REQUEST WAS NOT GRANTED; BUT I (FO) THOUGHT THAT IT WAS AND PROCEEDED TO CLB TO FL350. OTHER CREWMEMBERS DID NOT NOTICE THAT I HAD CLBED UNTIL TAIPEI CTL ASKED US OUR ALT WHICH WAS THEN AT FL34.7 (34;700 FT). I THEN TURNED OFF THE XPONDER AND DSNDED TO FL330 WHICH WAS OUR CLRED ALT. TAIPEI CTL THEN ASKED US WHAT ALT WE WERE AT AND WE REPLIED FL330. TAIPEI CTLR THOUGHT THAT THEY HAD A PROB WITH THEIR RADAR AS WELL AS A PROB WITH OUR XPONDER. WE LET THEM BELIEVE THAT THE PROB WAS THEIRS. SUPPLEMENTAL INFO FROM ACN 301533: WHILE CRUISING AT FL330; I REQUESTED FL350 FROM THE CTR. I WAS TOLD THAT THEY WERE UNABLE TO APPROVE FL350 BECAUSE OF OPPOSITE DIRECTION TFC AT FL350; 100 NM AHEAD OF US. I REPLIED 'ROGER' AND FORGOT ABOUT IT FOR THE TIME BEING. APPROX 4 MINS LATER I NOTICED THAT MY ALTIMETER READ FL350; AND REALIZED THAT THE COPLT (WHO WAS FLYING THE AIRPLANE); HAD MISUNDERSTOOD THE ATC DENIAL OF OUR REQUEST; AND HAD MISTAKENLY CLBED THE ACFT TO FL350. WE IMMEDIATELY DSNDED TO FL330 AND CONFIRMED TO ATC THAT WE WERE LEVEL FL330.