Pilot reported a communication issue resulted in an altitude deviation.

Attributes
ACN	1744199
Time
Date	202005
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Light Transport
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Captain
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Instrument
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 8000 Flight Crew Type 250
Events
Anomaly	ATC Issue All Types Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance

Narrative:

Enroute; we were cruising at 14;000 feet awaiting a climb (planned FL340). My first officer and I heard us cleared to FL270 from center. My first officer 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 first officer and I discussed the event and still believed that our tail number received the clearance.

Original NASA ASRS Text

Title: Pilot reported a communication issue resulted in an altitude deviation.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.