Check your iPhone settings to make sure that cellular data is active or switched on if you haven't previously. Navigate to Settings-> Cellular to do so. If necessary, toggle the switch to turn the function ON. Meanwhile, navigate to Settings-> Cellular-> Cellular Data Options-> Data Roaming if you're travelling overseas and encountering issues with your iPhone 7 Plus's cellular network. Ensure that the Data Roaming option is turned on.
Update your iOS to the most recent version.
If you haven't already done so, you should download the newest iOS update for your iPhone 7 Plus right now. Given that the problem remains despite performing all of the above steps, it's conceivable that a software defect is causing serious weaknesses, notably in the iPhone's network operations. Installing the most recent iOS update could be able to assist if this is the problem.iOS 10.3.3 is available for download, and it offers bug fixes and security updates for your iPhone. Go to Apple's official support page for further information.
