Old thread and I'm dusting it off for something I just figured out.
I have a smart phone, specifically an iPhone 4S. There is a plethora of calling apps out there available for the low low price of free and some higher end apps for a couple bucks.
Thanks to my modern tech savvy teens and their fancy Bluetooth devices including external wireless speakers, I've found iPhone+Bluetooth device = electronic call!
Some apps have adds, some you can hear a faint electric noise running under the call. Looks like some of the not free apps have other features which allow the calls to be customized to some degree.
The speaker I'm using runs to 70db I think. Don't know if that's enough but one guy told me most people call too loudly anyway and that it's probably fine.