ACR LTT RESPONDED TO CLRNC FOR ANOTHER ACR WITH SAME FLT NUMBER AND DEVIATED FROM ASSIGNED ALT.

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I WAS TALKING TO COMPANY ON THE #2 RADIO; GIVING OUR STANDARD IN RANGE CALL. WHEN I SWITCHED BACK TO #1 RADIO I ASKED THE COPLT IF THERE WERE ANY CHANGES. HE INFORMED ME WE HAD BEEN CLRED TO 3000' WHICH HE SET IN THE ALT REMINDER. APPROX 1 MIN LATER APCH ASKED OUR ALT. I REPLIED; '3000' ASSIGNED.' HE INFORMED ME THAT THAT ALT WAS FOR ANOTHER ACFT WITH THE SAME CALL NUMBERS; BUT A DIFFERENT COMPANY. THE CTLR APOLOGIZED SEVERAL TIMES FOR NOT INFORMING US THAT THE OTHER ACFT WAS ON THE FREQ. HE THEN TOLD US TO MAINTAIN 3000'; SINCE WE WERE NEEDED DOWN AT THAT ALT SHORTLY ANYWAY. WE SHOULD HAVE BEEN INFORMED ABOUT THE OTHER ACFT BY THE CTLR. ALSO; IF 2 SIMILAR CALL SIGNS ARE ON THE SAME FREQ; THE CTLR MUST STATE THE COMPANY NAME MORE CLEARLY IF NOT TWICE. I ALSO FEEL THAT PLTS SHOULD LISTEN MORE CLOSELY AND SHOULD NOT ANTICIPATE CTLR'S CLRNCS. THIS WAY THEY WILL BE MORE INCLINED TO QUESTION A CALL SIGN NOT HEARD CLEARLY OVER THE RADIO. IT WOULD NOT BE ASSUMED IT WAS FOR THEM JUST BECAUSE IT SOUNDS CLOSE. SUPPLEMENTAL INFO FROM ACN 82522: CTLR ACKNOWLEDGED CONFUSION OVER FLT NUMBERS. AFTER THAT THE CTLR SAID THE NAME OF THE AIRLINE; THE FLT NUMBER AND AIRLINE NAME AGAIN WHENEVER TALKING TO US OR THE OTHER AIRLINE WITH THE SAME NUMBER. I SOMETIMES FIND THE BOS CTLRS A BIT MORE DIFFICULT TO UNDERSTAND THAN MOST OTHERS. SOME SEEM TO CUT OFF THE BEGINNINGS OF THEIR TRANSMISSIONS.