Apple has released a new version of their software for the iPhone 7, the update is iOS 10.0.3 and it comes with a fix for a bug related to cellular connectivity.
The software update is designed to fix a problem where some owners of the iPhone 7 would lose cellular connectivity for mobile date, the update is around 75MB in size.
If you have been having problems where you data signal would drop off on your iPhone 7 or 7 Plus then this update should fix the issue.
The iOS 10.0.3 software update should be available for your iPhone 8 as of now, you can check if it is available by going to Settings > General > Software Update.
Source Apple