CAPT OF ACR USES CALL SIGN FROM PREVIOUS FLT.

Narrative

COPLT WAS DOING THE RADIO WORK. HE TURNED THE RADIOS OVER TO ME SO HE COULD DO A PA. I ACKNOWLEDGED A FREQ CHANGE. I THEN CHKED IN TO THE NEW FREQ USING THE CALL SIGN OF THE PREVIOUS FLT. CTLR; WHO I THINK WAS EXPECTING ME; GAVE ME A CLRNC FOR THE CORRECT CALL SIGN; 'CLB TO FL230.' I ACKNOWLEDGED; APOLOGIZED FOR THE MISTAKE; AND CONTINUED WITHOUT INCIDENT. IN RETROSPECT; I FEEL I WAS TOO QUICK TO ACCEPT THE CLRNC. I SHOULD HAVE STOPPED FOR A MOMENT; CONFIRMED MY CALL SIGN ; AND RECONFIRMED THE CLRNC. WHY? BECAUSE IN THIS SIT I COULD HAVE EASILY TAKEN SOMEONE ELSE'S CLRNC. THEN I WOULD HAVE HAD AN ALT VIOLATION. IN THE FUTURE; I WILL HAVE A PIECE OF PAPER WITH THE CORRECT CALL SIGN ALWAYS SITTING IN FRONT OF ME. THIS IS IMPORTANT FOR AIRLINE PLTS; BECAUSE THEIR CALL SIGNS ARE USUALLY CHANGING FREQUENTLY. ALSO; IT'S WORTH NOTHING THAT THIS WAS THE LAST FLT OF A 4-DAY TRIP. FINALLY; KEEP IN MIND THAT YOU LOSE YOUR SYS OF DOUBLE- CHK WHEN 1 PLT IS OFF THE AIR GETTING ATIS; DOING A PA; OR TALKING WITH COMPANY.