Basically, you don't need to do setup again to connect TV to internet via previously connected (last) 3G Dongle because the Access Point Name has been saved on TV.
It will be connected with a network automatically when 3G Dongle is inserted.
But when you use another dongle, you need to do the setup as follow:
Change [Access Point Selection] after inserting the dongle.
- Select HOME → Settings → Network → Mobile Network Set-up → Access Point Set-up → Access Point Selection.
- Select Access Point 2 or Access Point 3.
This TV can save up to 3 Access Point, so if you would like to add another 3G dongle when all Access Point has been used, you need to delete one of registered dongle data before inserting the dongle. And then select Access Point you want to use in Access Point Selection.