The reason for this message "A server with the specified host name could not be found" in my iPhone 6 (IOS 11)?

I get a pop-up message saying "A server with the specified host name could not be found", whenever I try to access Apple Music (Online). I am using Airtel Internet (4G). I can easily stream YouTube videos, I receive that annoying message. I am using iPhone 6 with IOS 11. And everything about the internet connection is totally fine, as I've explained the issues, above. If there are any technical settings that I should change/modify in my iPhone(iOS 11), PLEASE let me know.