I believe it's an outgoing (only) line for a telemarketing company [Wares & Associates] hired to help non-profits fundraise during their telethons, giving calls, etc.
Because their calls are designed to be outgoing, only, it's hard to call back and get the same person who called you (also why they don't leave vmails—they don't really have assigned extensions for each call desk), and several of their extensions will return a busy signal. Their general line is 626-398-4700, but other reviews say it's difficult to be routed correctly from the main line.