B737-700
Flight Crew Last 90 Days 170; Flight Crew Type 170
Communication Breakdown
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Human Factors; Company Policy
While cruising at FL380; I thought I heard our call sign and said to the Captain; 'I think that was us.' We didn't respond and; a few seconds later; ATC said; 'Company Flight Number; descend to FL320.' I replied to the clearance and started a VNAV descent. At 36;500 FT; ATC instructed us to climb to FL380. The Captain told ATC we would have to climb and that we were descending to FL320. ATC then asked if we wanted FL360. The Captain said yes. ATC gave us FL360 and also stated we may have taken someone else's call.
Air Carrier initiated a descent but was questioned by ATC regarding a possible same company mix-up; i.e. the clearance was issued to a company flight.