You can manually configure the DNS servers in your iOS settings. Here is how:
- Open Settings;
- Tap on Wi-Fi. If it's switched off, turn it on;
- Pick a Wi-Fi network and tap on the blue i icon;
- Tap Configure DNS and select Manual;
- Tap Add Server and add these DNS addresses:
103.86.96.100
103.86.99.100
- Tap Save.