What changes
Instead of relying only on the local cellular radio link, the phone can establish a secure carrier-supported connection over Wi‑Fi and the internet.
What affects quality
Wi‑Fi signal, local congestion, ISP latency/loss and the carrier's service path can affect call quality. A high download speed alone does not guarantee stable voice performance.
Moving between Wi‑Fi and cellular
Handoff behavior varies by carrier, device and network conditions. Do not assume every call will move seamlessly between Wi‑Fi and cellular coverage.
Emergency calling
Emergency-calling requirements and location/address handling vary by jurisdiction and carrier. Follow your carrier's current setup instructions for emergency address information.
Networking capabilities vary by hardware, firmware, ISP, country and radio environment. Settings names differ among manufacturers, so use your device's current documentation for product-specific changes.