My phone has DNS problem

[AC Question]

I bought new Huawei HG532D router for my new ADSL2 connection. I did all the startup procedure. I am able to browse internet perfectly on my laptop and PC. But when I connect to my Moto G2 it always shows DNS error on all browsers and Youtube stops working completely. Sometime internet works but mostly it gives me that DNS Probe error on Chrome. I tried OpenDNS and Google DNS on my router and phone. Also tried setting static ip. For few minutes internet starts to work when I turn off & turn on WiFi on my phone. I tried multiple factory reset on phone and router. I also switched to my old Nesux 5 but that problem is still there. The thing that annoys me is that on my sister's Nexus 5x internet works much better than my phone. But she also faces same problem when watching Youtube and occasionaly sees that DNS error on her phone when browsing. What should I do ?