Save yourself money and move to one of the other ISP like Axxess or Webafrica.
I started with Telkomsa, moved to Axxess and am now with Webafrica - because Webafrica is better value for money at the top end.
Edit: Not sure if Axxess allows multiple logins.
Do consider using NAT - a NAT router is cheap, and it is a decent dedicated firewall as well - working as good as you are able to set it up.