I am unable to do update and I have space also
I am unable to update and I have sufficient storge.
iPhone 6s Plus, iOS 11
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Your products list (at the bottom of your question) shows that you have an iPhone 6s Plus, running iOS 11.
Should be this case, iOS 11 is a very old operating system version and you won't be able to update the device to the latest iOS (now 15.3) wirelessly.
I suggest that you update it via computer (if you don't have a computer borrow one from your friends/neighbors/relatives, or ask for help at an Apple Store or Authorized Service Provider), then learn how to update your device manually if you're using a Mac with macOS Catalina or later, or if you're using a Mac with macOS Mojave or earlier or a Windows PC.
If you still get no help, contact Apple Support directly, using this link:--> Get Support
Regards
Giulio