A few years some ATT 911 calls failed due to VoLTE issues. The FCC punished them. So now they refuse to enable VoLTE except on blessed phones. https://www.fcc.

A few years some ATT 911 calls failed due to VoLTE issues. The FCC punished them. So now they refuse to enable VoLTE except on blessed phones. https://www.fcc.gov/document/final-report-march-8-2017-att-mobility-volte-911-outage https://www.fcc.gov/document/final-report-march-8-2017-att-m... The US cellular market still involves bundling handset and service, sold in physical stores. Bringing your own phone is deviating from the happy path. Carriers are not motivated to fix interoperability bugs because it increases customer churn.