ENRTE CIVIL JET AT 11000 FT WITH ZOB; RECEIVED FREQ CHANGE INSTRUCTIONS FROM AN APPARENT PHANTOM CTLR.

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SETTING UP THE COCKPIT FOR AN ILS TO MINIMUMS AT CLE. THE PNF (CAPT) WAS RECHKING ATIS ON COM #1 WHILE THE FO (PF) TOOK THE DUTIES OF PRIMARY RADIO ON COM #2. COM #2 WAS UP ZOB. A FREQ SWITCH WAS CALLED BY ZOB (OR SO I THOUGHT) FOR 'ACFT X; CONTACT CLEVELAND APCH ON 120.6; ALTIMETER IS XXX.XX.' I ROGERED THE FREQ CHANGE AND INSTRUCTED THE PNF; WHO HAD JUST FINISHED WITH ATIS; TO CHK US IN WITH APCH ON COM #2. HE TRIED TWICE ON 120.6 AND GOT NO RESPONSE. SO; WE WENT BACK TO OUR LAST ASSIGNED FREQ WITH ZOB. CTR ADVISED THAT THEY HAD SIMILAR FREQ MISCOMS FROM 'SOMEONE ON THE GND' AND THAT '120.6' WAS A 'PHANTOM CTLR.' WE WERE INSTRUCTED TO REMAIN WITH CTR AND A FEW MI LATER WERE HANDED TO APCH AND BEGAN THE ILS TO CLE WITHOUT FURTHER INCIDENT. AT THE HOTEL LATER THAT NIGHT; COMPANY CALLED THE CAPT AND A CONFERENCE CALL WAS MADE WITH ZOB TO DISCUSS THE INCIDENT. AT NO TIME WERE WE VECTORED OFF COURSE OR GIVEN AN ALT CHANGE. ONCE ON 120.6; NO COM WAS MADE WITH THE 'PHANTOM CTLR' AND WE RETURNED TO THE 'REAL' CTLR (ZOB) WITHOUT INCIDENT OTHER THAN A FEW MINS OF RADIO FREQ CONFUSION.