Date: 202104
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Captain; Pilot Not Flying
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: While being radar vectored to the visual final for Runway XX at ZZZ; Approach Control issued a descent to 6;000 feet MSL. We read back the clearance and proceeded to descend to 6;000 feet MSL. The Captain did observe that we seemed closer to some radio Towers on a hill than what would appear normal; but we received no GPWS Alerts. We continued on vectors and flew an uneventful approach and landing. After a call from Tower a few hours later; it was explained that the descent clearance to 6;000 feet was issued to a (other carrier X) whose readback was on a different Approach Control frequency. Our readback to that clearance as Company A (very similar sounding call sign) must have occurred at the same moment as (other carrier's) reply. Since the (other carrier X) aircraft had been on a different approach frequency; we had yet to hear any other communications to or from that aircraft; and ATC had not issued a caution for the similar sounding call signs. Additionally; ATC did not issue a low altitude warning if we had gone below the Minimum Vector Altitude in the sector we were within.When managing multiple frequencies; ATC should ensure that aircraft with similar call signs are alerted to possible miss interpretations. Furthermore; ATC should minimize the use of simulcasting on multiple Approach frequencies and consolidate traffic to one radio frequency.


Second narrative: We were being vectored for the visual approach to Runway XX at ZZZ from the east. ZZZ Approach Control issued a clearance to 6;000 feet MSL. We were later contacted that the clearance was for (other carrier) X; on another frequency and not for Company A. The clearance apparently took us below the MVA for that sector. The Controller was controlling multiple frequencies (he was busy) and never advised us of similar sounding call signs. We did not receive any terrain cautions from the aircraft or Controller.  The subsequent approach and landing were uneventful.Listening during communications is always the most important.  Being advised of similar sounding call signs is an important step to help alleviate threats and for Crews to be more vigilant.


Synopsis: B737-700 flight crew reported a CFIT event during a visual approach due to an ATC communications breakdown between flight crew and Approach Control who was working multiple frequencies with similar callsigns.