Internet access

Please go to your Wifi settings and connect and if you've connected before to the network, do forget this network or reset your iPhone network.

If your iPhone, iPad or iPod touch won't connect to a Wi-Fi network – Apple Support (UK)

visit that site it will guide you through on how you can reset your network

See if this helps: If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi + Cellular) - Apple Support

Since Personal hotspot is a specific cellular carrier service, I suggest that you contact them and explain your problem.

Regards

Giulio