Can't update my iPhone 7

my Phone won’t update, n now my cellular won’t work because of it. My phone won’t update, I’ve tried to update through iTunes, deleting the update and redownloading and going to another WiFi source. It just keeps saying error can’t download. THIS IS RIDICULOUS it’s been 5 hrs now of trying because I HAVE to have my phone for work etc.

[Re-Titled by Moderator]