Wikipedia
First Call
First Call was an American contemporary Christian music (CCM) group, originally consisting of Mel Tunney, Marty McCall, and Bonnie Keen. Mel's husband, Dick Tunney, acted as the arranger and producer for many of the group's early projects.
Usage examples of "first call".
I have a precision mercury thermometer on order from the Essen Instrument Company thanks to my son, but they have a six month backlog in all of their orders, and their priority customers in Essen have first call on any emergency equipment.