Date: 202008
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise; Initial Approach
Airspace: Class B ZZZ
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: Descending into ZZZ via the ZZZZZ2 it appears there was confusion caused by similar sounding call-signs.  Although our controller did not specifically identify whether he or I made the mistake; it seemed like our flight ended up on a heading and descending to an altitude that was not intended.We were operating Flight ABCD.  The flight had been uneventful and we were 'DESCENDING VIA' the ZZZZZ2 from the ZZZZZ transition into ZZZ.  We were handed off to ZZZ Approach who appeared to be moderately busy on our frequency.  Both the FO and I heard ABDC also on the frequency.  At approximately ZZZZZ1; the Controller issued us a clearance to 11;000 feet at 230 knots.  I acknowledged the clearance. The FO remarked that was a 'different' speed and altitude than we typically received on this arrival.  Shortly thereafter; we both thought we heard the Controller issue us; ABCD; a left turn to a heading of 330 and a descent to 8;000 feet.  I acknowledged the clearance and we executed the clearance.  Within a minute; the Controller came onto the frequency and I believe he said (without a mentioning a callsign) 'you took the other's call;' then told us to stop descent at 11;000 feet - which we were just descending through.  The FO; without hesitation; disabled the Autopilot and stopped the descent and maintained 11;000 feet.  The Controller then issued a turn back to 090.  We made the turn and reset the automation.  Shortly thereafter; we were cleared direct to ZZZZZ2 and we continued the flight without further event.  We both did notice that every subsequent Controller seemed to excessively emphasize our callsign for the remainder of the flight which makes me suspect that perhaps I did 'take' ABDC's call (330 Heading / 8000 feet MSL).  However; the FO and I both felt relatively sure that we had heard our callsign.     Initially I thought it may have been poor planning; that put two similar sounding call-signs into the same airport at the same time without some mitigating tool like an 'A' designator after the normal call-sign.  However; some after-the-fact research seems to indicate that ABDC had incurred a long delay that put our flights in proximity.  These flights would not normally operate in the approach environment at the same time.  With the COVID-19 pandemic; we have seen FAA ATC consolidate many sectors.  In this case; the Approach Controller was - at the very least - working arrivals from both the southwest and southeast.  As flight schedules have increased a bit in July and August; I have had several experiences where Controller - and particularly frequency - saturation have occurred. Perhaps increasing ATC staffing levels - particularly in the approach environment would be appropriate.




Synopsis: Air Carrier Captain reported taking an ATC clearance for a similar sounding aircraft on the same frequency. The Captain reported the Controller was working multiple sectors at the time.