Light Transport
Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 150; Flight Crew Total 8000; Flight Crew Type 250
Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Environment - Non Weather Related; Human Factors; Procedure
Enroute; we were cruising at 14;000 feet awaiting a climb (planned FL340). My FO and I heard us cleared to FL270 from Center. My FO read the climb clearance back without comment from ATC. We began a climb and sometime just above 16;000 feet; ATC came on frequency with instructions to descend; that we were not cleared to climb. We immediately began a descent. I apologized and explained what we heard and read back. ATC did not respond. Remainder of interaction with Controller was uneventful; as was the remainder of the flight.With the pandemic; prior discussions with ATC informed me that less traffic volume has resulted in Controllers covering more simultaneous sectors. I'm wondering if the climb clearance was given to an aircraft on a different frequency (with a similar call sign) such that we heard no other aircraft read back the clearance; further reinforcing our belief that the clearance was for us. My FO and I discussed the event and still believed that our tail number received the clearance.
Pilot reported a communication issue resulted in an altitude deviation.