When Beca enters the radio station for the first time, the station's frequency is written on the outside window (85.7) but DJ Luke's voice is heard in the background saying the frequency is 95.7 (.."music for the independent mind".)
When the guys come in to announce there's no one left to audition, Aubrey and Chloe have no one sitting behind them. The shot changes and there are 2 people sitting behind them. When Beca enters, those people disappear again.
Twice we see the sign on the door of the radio station showing 85.7 FM while we hear it advertised as 95.7 FM. (Also, frequencies below 87.5 FM are not used in the United States.) Also, radio stations based at educational institutions in the United States are based between 87.5 and 91.5 FM.