- Ensure you have enabled Wi-Fi calling by going to Settings > Phone > Wi-Fi Calling > check the toggle for Wi-Fi Calling.
- Try restarting the phone and modem and turning on and off Airplane mode.
- If it doesn’t help, change the DNS or reset network settings.
Fix 1: Eject SIM and Disable Mobile Data
If Wi-Fi calling is giving you trouble, remove the SIM card from your iPhone for about 30 seconds. Clean it with a microfiber cloth. Then, insert it back. Post this, disable mobile data and try using Wi-Fi calling. This should probably fix the issue.
Fix 2: Change DNS
Often, Wi-Fi calling doesn’t work properly due to a DNS server issue. So, change the DNS server for your Wi-Fi network as follows.
Step 1 : Open Settings > go to Wi-Fi > tap on the i icon next to your Wi-Fi network.
Step 2 : Tap on Configure DNS . If it’s showing Automatic, tap on Manual .
Step 3 : Now, enter 8.8.8.8 or 8.8.4.4 (Google’s servers). However, if it is on Manual, select Automatic .

Fix 3: Reset Network Settings
Lastly, if nothing works, try resetting network settings. To do this, go to Settings > General > Reset > Reset Network Settings .
