A300 pilot reported losing communication with ATC resulting in flight towards terrain. Communication was reestablished and ATC climbed the aircraft to a safe altitude. The flight arrived safely at their destination.

Narrative

Flight was enroute from ZZZ1 to ZZZ. Abeam ZZZ2; Center issued a descent clearance and; subsequent; frequency change to 120.15 (ZZZ approach). Initial communication was nominal and clearances were issued to descend to 3K MSL. Aircraft was vectored onto a Right Downwind north of the airport. Crew complied with clearances and observed other traffic arriving from the opposite direction. Unbeknownst to us; Approach Control attempted to vector us for the approach but we could not hear the clearances at 3000 ft on downwind. As we continued on our last assigned heading and frequency; we heard ZZZ approach call us on guard frequency trying to reach us. We responded on guard and were given a clearance to immediately climb 100 ft to 3100 ft MSL for MSA requirements. After reestablishing communication on the correct frequency; the controller explained that center had assigned us an incorrect frequency which serves the ZZZ3 area; not ZZZ. I called the approach control facility after landing and confirmed there was no loss of separation during the event. It seemed that this was not an isolated event.