Looks like a variation on the film Ransom (turning the tables on the kidnappers).
The two same camera angles over and over were tiresome. Some closeups of the piano player would have been a better choice. Why was the caller wearing that mask?
You don't need to use a union crew for a SAG shoot. You can use union crew members but don't become a signatory with the IATSE otherwise all of your crew MUST then be union.
Look at the book Creative Producing from A to Z by Schreibman which has a lot of info on union/non-union issues.
Mark