I’m not able to install latest software update 15.6.1 in my iphone 7 plus please help me to solve this
Please help me how to install new software update on my phone
You need to fix that No Service issue first if you want to update wirelessly.
If you see No Service or Searching on your iPhone or iPad - Apple Support
Otherwise try updating using a computer.
Update using your computer -
Update iOS on iPhone - Apple Support