Is it possible to check the DNS server you're using on the iphone? on windows, you'd use something like ipconfig /all to see the dns server you're hitting.

What would u do on an iphone or mobile device?
You can see the DNS assigned to the Wi-Fi in Settings → Wi-Fi, then tapping on the blue arrow next to the network you're connected to. I'm not sure if it's possible to do the same for the cellular connection however.