You can manually configure the DNS servers in your iOS settings. Here are the steps:
- Open the Settings app;
- 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.