I have already updated my phone fully. Reset network settings and all of these things. Nothing is working. I saw that this is a common issue with iPhone 7 (I bought my phone from America) and it should be fixed for free. I currently live in Bahrain and they said that the branch here can’t fix it or compensate me in any way. I even contacted apple support and they said they can’t do anything from their side.
iPhone 7
Follow the instructions here, If you see a Cellular Update Failed or Apple Pay Not Available alert after iOS update or restart - Apple Support
You can manually check for and install a carrier settings update with these steps: Make sure your device is connected to a Wi-Fi or cellular network. Tap Settings > General > About. If an update is available, you'll see an option to update your carrier settings.
Update your carrier settings on your iPhone or iPad - Apple Support
I have already done that. It’s model A1660 and apparently it’s a manufacturer fault in models A1660 produced from Sep 2016 onwards in a few countries including the US which is where I got it from.
An update is required to use cellular data on this phone
