Sony phone has a "Tethering error" prompt?
The problem is the APN settings.
Check all the APN settings on your phone.
If one of them has "dun" in "APN Type" field, your phone will use this APN setting for tethering.
Either remove this APN setting completely or if you can not remove the setting, clear this APN setting
field.
None of the APN settings should have "dun" on their APN Type field unless you want to set a different
APN account for tethering.
APN Type "default,supl" for the main APN setting is enough for most of the cases.