All I have is a laptop can I use that?
No service error code
can I use a laptop without iTunes to fix my phone
iPhone 7, iOS 14
You need iTunes on a computer to do any kind of support work on the phone, such as restore, etc. See this for No Service issues, If you see No Service or Searching on your iPhone or iPad - Apple Support and see this for iPhone 7 issues. iPhone 7 Repair Program for "No Service" Issues - Apple Support