After two hours, I have solved the issue.
The problem was, there were two default APNs.
One for tethering, one for mobile phone network connection.
The solution was to add "defult" apn type to the tethering apn and remove the mobile phone one.
To use hotspot in the house with more than 10 devices, I found something that works with a little money. What I end up using were some old devices that I had laying around the house. What you need are two items: a repeater, and also an old router.
If you have to use a repeater alone, use it in bridge mode so it will not be assigning new IP addresses. The IP ...
Your phone uses a different type of connection (DUN) to send tethered data but you can make the provider treat all traffic as if it is non-tethered:
adb shell settings put global tether_dun_required 0
When enabling tethering on Android, the OS will first do a provisioning check with the carrier to determine if your plan allows tethering. You can remove this ...