A320 DESCENDING INTO SAC IS CONFUSED BY ZOA WITH COMPANY TFC LNDG SFO.

Narrative

WE HAD ANOTHER ACFT GOING INTO SFO WITH SIMILAR CALL SIGN WITH OURS; THAT WAS CONFUSED WITH OUR DSCNT INTO SACRAMENTO. WE REQUESTED LOWER ALT TO MAKE THE SWR VORTAC AT FL240; OR BELOW. ZOA DSNDED US TO FL310 AND SAID WE WOULD NOT GET THAT RESTR AT SWR. WE FINALLY GOT CLRNC DOWN TO FL240 AND A FREQ CHANGE TO LOWER SECTOR. WHEN THE FO CHKED IN; HE GAVE US LOWER ALT OF 14000 FT AND AN ALTIMETER SETTING FOR SFO. FO SAID THAT WAS ODD THAT THEY GAVE US SFO ALT 29.80. THIS WAS OUR FIRST CLUE; BUT WE DID NOT DO ANYTHING ABOUT IT. AS WE CONTINUED INTO SACRAMENTO; WE GOT A TCASII ALERT AND GOT A VISUAL ON THAT ACFT (LIGHT TWIN). THIS WAS ABOUT THE TIME ZOA DISCOVERED OUR (IE; HIS AND OURS) MISTAKE. WE REQUESTED A LOWER ALT AND CTR SAID; 'ACR X I GAVE YOU 11000 FT.' WE SAID; 'NO; ACR Y REQUESTED LOWER.' CTR SAID; 'WHERE ARE YOU?' I SAID THAT WE ARE DSNDING INTO SACRAMENTO. HE GAVE US A NEW FREQ FOR NORCAL APCH; WHICH GAVE US 12000 FT AND HEADING 250 DEGS. THEY ALSO ADVISED US THAT THE TWIN HAD A VISUAL ON US. AS WE STARTED OUT DSCNT TO 12000 FT; WE GOT AN RA; BUT OUR DSCNT WAS ALREADY BELOW THE REQUIRED BY THE RA; WHICH SHORTLY CAME BACK WITH; CLR OF CONFLICT. WE CONTINUED INTO SACRAMENTO TO NORMAL LNDG. THIS WAS CAUSED BY SIMILAR CALL SIGNS AND CTR NOT NOTICING AT OUR CHK IN; AND GAVE US DSCNT MEANT FOR ACR Y INTO SFO.