Update
The new update for ipad and iphone seems to have destroyed the possibilty for internet sharing ( pair cuopling). Do you have the same problem?
Question marked as
If you mean the iPhone hotspot that allows you to have share internet with your iPad, you should contact your cell phone carrier. They may have a "Carrier Update" available.
To see if you have such an update available, open Settings, tap General and tap About. If any carrier update is available, you will be prompted to update.