VoIP.ms
Well, it finally happened. I got and installed replacement batteries for my payphone, but it still did not work completely. My OBI200 ATA finally quit working with Google Voice, as it has been end-of-support for some time now. I knew it was coming, but hadn't made a backup plan. So I found an inexpensive VoIP provider, VoIP.ms, and managed to get it going fairly quickly. There are walkthroughs for configuring a ton of different devices, so a quick factory-reset of the OBI and following a quick guide, and all is good. It was something like $0.85 for the DID, and around $0.009/minute for calls. I think they offer "unlimited" plans as well. They also have a basic Cisco IOS configuration for their service, so I think I may have a provider to use with my dial-up ISP project.