In my iPhone if you specify the settings for mobile Internet
then disappears modem mode (possibility to distribute the Internet to other devices), but the Internet works consistently.
the hotspot appears, but the Internet is working through the stump deck — that is, there is no (3G or edge while burning) and helps only restart the phone.
There are separate settings for tethering in the settings of the phone, but gdata/gdata fit, and that is where you need to enter I can't find it.
Calling support did not help — he advised me to go to Tverskaya street in Central office.
The result: either a stable mobile Internet without the ability to distribute to other devices, or periodic stuttering.