Narrative:

I was PF, engaged autoplt at 500 ft AGL. On loupe 9 rbl transition. As I started turn at 1.8 DME, bay approach advised us of VFR traffic at 3-4 O'clock, leveling at 4000 ft. We had the traffic on TCASII but no visual because we were climbing out of overcast. The captain was talking to bay approach about the traffic and concerned that VFR traffic would be at 4000 ft. Bay informed him that the altitude of the traffic was assigned by approach. Passing through about a 030 degree heading and 4000 ft, I spotted the traffic and the captain called bay approach with traffic in sight. Just as the radio transmission was ending the autoplt and pms was leveling the aircraft at 5000 ft and 200 KTS. Without pause bay approach came back with climb and maintain 12000 ft to us. The captain read back 'air carrier xyz to 12000 ft.' we set the altitude alert to 12000 ft and called out 12000 ft, set and armed. We both expected this since we were clear of the traffic and many times they (bay approach) give us an early climb. Passing through 6200 ft MSL and accelerating to 250 KTS, bay approach calls us and asks our altitude. We respond with 6300 ft for 12000 ft. Bay then says your assigned altitude was 5000 ft, and tells us to level off. We leveled at 7000 ft. Air carrier xab was also on the frequency ahead of us and bay approach said the climb was for him. But the captain and I are positive bay approach said 'air carrier xyz.' we followed all procedures of our company's altitude awareness of both pilots verifying altitude settings. We believe that ATC used the wrong call sign. ATC has confused our call signs a number of times in the past. Many times we will have 2 or 3 air carrier flts on the same frequency with similar numbers like xyz and xab or abc and acb. Usually one of us will catch it and alert ATC or each other before something happens. But this occurrence was so clear. The captain was talking to ATC and without pause bay approach made an altitude assignment, which we read back and heard no other transmission until bay approach queried our altitude. Coming back from pdx we got bay approach's phone number and called to talk to a supervisor. She informed us that no reports were made. We have told our company about the call sign problem but I haven't seen any changes.

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Original NASA ASRS Text

Title: CONFUSION BY ACR FLC ON WHICH CALL SIGN WAS USED BY DEP CTLR. ALTDEV ALT EXCURSION.

Narrative: I WAS PF, ENGAGED AUTOPLT AT 500 FT AGL. ON LOUPE 9 RBL TRANSITION. AS I STARTED TURN AT 1.8 DME, BAY APCH ADVISED US OF VFR TFC AT 3-4 O'CLOCK, LEVELING AT 4000 FT. WE HAD THE TFC ON TCASII BUT NO VISUAL BECAUSE WE WERE CLBING OUT OF OVCST. THE CAPT WAS TALKING TO BAY APCH ABOUT THE TFC AND CONCERNED THAT VFR TFC WOULD BE AT 4000 FT. BAY INFORMED HIM THAT THE ALT OF THE TFC WAS ASSIGNED BY APCH. PASSING THROUGH ABOUT A 030 DEG HDG AND 4000 FT, I SPOTTED THE TFC AND THE CAPT CALLED BAY APCH WITH TFC IN SIGHT. JUST AS THE RADIO XMISSION WAS ENDING THE AUTOPLT AND PMS WAS LEVELING THE ACFT AT 5000 FT AND 200 KTS. WITHOUT PAUSE BAY APCH CAME BACK WITH CLB AND MAINTAIN 12000 FT TO US. THE CAPT READ BACK 'ACR XYZ TO 12000 FT.' WE SET THE ALT ALERT TO 12000 FT AND CALLED OUT 12000 FT, SET AND ARMED. WE BOTH EXPECTED THIS SINCE WE WERE CLR OF THE TFC AND MANY TIMES THEY (BAY APCH) GIVE US AN EARLY CLB. PASSING THROUGH 6200 FT MSL AND ACCELERATING TO 250 KTS, BAY APCH CALLS US AND ASKS OUR ALT. WE RESPOND WITH 6300 FT FOR 12000 FT. BAY THEN SAYS YOUR ASSIGNED ALT WAS 5000 FT, AND TELLS US TO LEVEL OFF. WE LEVELED AT 7000 FT. ACR XAB WAS ALSO ON THE FREQ AHEAD OF US AND BAY APCH SAID THE CLB WAS FOR HIM. BUT THE CAPT AND I ARE POSITIVE BAY APCH SAID 'ACR XYZ.' WE FOLLOWED ALL PROCS OF OUR COMPANY'S ALT AWARENESS OF BOTH PLTS VERIFYING ALT SETTINGS. WE BELIEVE THAT ATC USED THE WRONG CALL SIGN. ATC HAS CONFUSED OUR CALL SIGNS A NUMBER OF TIMES IN THE PAST. MANY TIMES WE WILL HAVE 2 OR 3 ACR FLTS ON THE SAME FREQ WITH SIMILAR NUMBERS LIKE XYZ AND XAB OR ABC AND ACB. USUALLY ONE OF US WILL CATCH IT AND ALERT ATC OR EACH OTHER BEFORE SOMETHING HAPPENS. BUT THIS OCCURRENCE WAS SO CLR. THE CAPT WAS TALKING TO ATC AND WITHOUT PAUSE BAY APCH MADE AN ALT ASSIGNMENT, WHICH WE READ BACK AND HEARD NO OTHER XMISSION UNTIL BAY APCH QUERIED OUR ALT. COMING BACK FROM PDX WE GOT BAY APCH'S PHONE NUMBER AND CALLED TO TALK TO A SUPVR. SHE INFORMED US THAT NO RPTS WERE MADE. WE HAVE TOLD OUR COMPANY ABOUT THE CALL SIGN PROB BUT I HAVEN'T SEEN ANY CHANGES.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.