I did these steps below to activate personal hotspot on iPhone 7 on iOS 10.3.1. I use Telkomsel network.
- Go to settings > Cellular > Cellular Data Options > Cellular Data Network.
- On Personal Hotspot section, write internet on the APN field.
- You can see Personal Hotspot is back on Settings.
Thanks to Jacob Hämmerle, adding internet to Personal Hotspot section only works.