C560 FLT CREW CLBS ABOVE ASSIGNED ALT BECAUSE OF CONFUSION WITH SIMILAR CALL SIGNS WITH N90 TRACON.

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JET XYZ WAS SCHEDULED FLT FROM MMU TO PHL. ACFT TOOK OFF OUT OF MMU ON SID. LEVELED ACFT AT 2000 FT AND WENT TO DEP CTL. WAS CLBED TO 3000 FT AND GIVEN HDG. HOWEVER; UNAWARE TO ME; THERE WAS ANOTHER BUSINESS JET XYZ ALSO ON FREQ. I APPARENTLY ANSWERED A FREQ CHANGE INTENDED FOR THE OTHER BUSINESS JET AND WENT TO THE NEW FREQ. I CHKED ON THE FREQ WITH MY CALL SIGN AND THE CTLR APPARENTLY THOUGHT I WAS THE OTHER BUSINESS JET AND TOLD ME TO CLB TO 12000 FT. WE INITIATED A CLB AND I BELIEVE REACHED 4300 FT WHEN THE OTHER BUSINESS JET PLT MADE BOTH ME AND THE CTLR AWARE OF THE MISTAKE. WE THEN STOPPED THE CLB AND MAINTAINED 4000 FT AND RETURNED TO THE PREVIOUS CTLR. HE THEN ISSUED ME ANOTHER FREQ CHANGE AND I WENT TO THE NEW FREQ AND WAS GIVEN A CLB TO 7000 FT. FLT CONTINUED WITHOUT FURTHER INCIDENT. I BELIEVE THE PROB WAS CAUSED BY THE SIMILARITY IN CALL SIGNS BOTH ENDING IN XYZ. I HAVE NOTICED IN THE PAST WHEN CTLRS REALIZE SIMILAR CALL SIGNS ON THEIR FREQ; THEY ADVISE BOTH ACFT TO AVOID CONFUSION. MY EXPERIENCE TO HEAR OUR CALL SIGN AND NOT KNOWING OF THE CALL SIGN OF THE OTHER BUSINESS JET XYZ CAUSED THIS ERROR.