Updatevand no service problem on iphone 7

What can I do have been trying to rectify a no service problem on an iphone 7, after doing a restore it tell me it cant connect to activation server and later it says I should update that an update is needs to be install, I restored with d most recent file, so I tried to do the update but it still downloading d whole ios fike 4.67gb again, mind you the no service for the sim card is still showing