The women singing the song are Justin and Jeremy Furstenfeld's mother and her coworkers singing along to "Calling You" in a voicemail to Justin when they heard the song playing on the radio at their office.
The female vocalists performing the song are Justin and Jeremy Furstenfeld's mother and her colleagues singing along to "Calling You" in a voicemail to Justin when they heard the song playing on the radio at their workplace.