Quite possibly, you can leave all the other fields empty, except the APN where you write prointernet.
If this does not work, you can try to fill in the following data:
Dialed number: *99#
User Name: empty
In case the VPN-connection starts not to work, I would like to ask you to call Helpson Support, because their experts are specialized in devices and settings. Helpson´s phone number is 0600 10100 (Mon-Fri 8-21 and Sat 9-17).
I hope that you are able to get VPN-connection working.