Apple controls the functionality available to Mobile Data users through the Carrier Settings.
iPad with Apple SIM
If you have the latest carrier settings on your iPad, you can use the Personal Hotspot feature on an iPad.
iPhone / iPad with GigSky SIM
The Personal Hotspot function is NOT available to GigSky on the iPhone or iPad with GigSky SIM. When iOS 11 is released, the Personal Hotspot function will be available when using the GigSky SIM on the iPad.