So I bought it from Vietnam, and I set it up in India with JIO Mobile Network. Everything was fine until I found that only on my iPhone 3 Pro Max, the internet is working, and in all other devices, it's saying no internet connection. Ii really screwed up .Why, I mean, why is it happening? Why work only on one device and not on other devices?If 
you face this kind of problem, please let me know the solution if you have figured it out