SMS 2FA is not just insecure, it's also hostile to mountain people

Summary

i have a friend — she's an old lady born and raised here in the western north carolina mountains. she hates computers, yes, but she's been willing to learn a lot and quickly after joining a big signal group chat that our shared local community uses to keep in touch. aside from memeing with the best of them in the group chat, she also maintains a large fish pond outside the house she built herself. this despite being in her 70s. she's an inspiration. she has a landline. it works great, and the landline phone hardware works great with her hearing aids. she's had it for years. spectrum has a monoply in our area so the landline and her cable internet service is with spectrum. she got a cell phone a few years ago. she got a smartphone basically because she had to to do basic life tasks, including joining the big signal group chat. at first she just used it on wifi, but quickly she decided she wanted to be able to use the phone everywhere so she got a cell phone plan from spectrum because they were already her ISP. spectrum mobile uses the verizon network — famed for its good rural coverage. this is where things started to go haywire. all her accounts on websites, things like email and bank accounts and health insurance and healthcare providers, they started trying to send her SMS messages in order to let her get into her accounts. the SMS codes don't work, because they don't come. she doesn't have cell service at her house. it's up in the mountains, sure, but it's not isolated. she lives 20 minutes from downtown asheville and she has lots of neighbors on her road. she turned on wifi calling on her phone. now she could receive SMS messages from friends and family, but 2FA codes still weren't coming through. i did some digging, and it turns out messages from 5 digit shortcodes often aren't supported over wifi calling. sometimes they are, but in her case they're clearly not. she has a current, stock iphone. she's using the spectrum-provided internet hardware. she knows how ...