*sigh* Sorry to hear that.
The only alternative I can think of for "simple" to set up, cheaper home phone service is to use a cellular wireless ATA (cellphone to home phone bridge). Unfortunately, I don't know of any models off the top of my head that are carrier unlocked or VoLTE capable with AT&T, Verizon, or especially T-Mobile... if I knew you had good T-Mo reception, and knew of an unlocked T-Mo VoLTE capable ATA, you could always stick in a US Mobile SIM and just get a voice only plan for under $10/month. Otherwise, if you're stuck with an AT&T device and MVNO, you're looking at $20/month. At that point, you might as well just throw money at Vonage or Ooma's full price service, where you may or may not still potentially have problems given some of the issues you're describing.
I'll be honest with you, telecomms in this country are a hot mess these days, and I suspect there's gonna be some unexpected changes within the next 12-18 months. Between the pending Verizon Wireless/America Movil merger, major legacy wireless network shutdowns from the big three, union rattlings for changing internet into a utility and the potential return of net neutrality, STIR/SHAKEN implementation with voice services, and Facebook's win in the Supreme Court basically making modern robocalling legal again due to poorly written 1980's legislation...
Yeah. I hope the changes are for the better, but the cracks and divides just keep widening.