During Noah's dinner party he mentions he listens to 98.3, a station on the FM dial. Later when Catherine is driving she tunes her the radio, presumably to 98.3. However, her truck's radio is an AM radio incapable of tuning the FM band.
When Catherine calls the radio station to tell her story, she is heard live on the air without a delay. Typically radio station callers are on a 5+ second delay to allow time for the DJ to cut out any inappropriate dialogue.