I dealt with this issue a few weeks ago. The helpline was of no use, so I talked to the nodal officer and explained the issue to him. He insisted that logging in through the portal will get me a public IP like before, but it's not convenient logging in every 24 hours (ACT has a 24 hour session limit on both PPPoE and portal login). I persisted and he noted down a complaint.
Next day I received a call from a helpful engineer, who told me she will associate my
MAC address to my account and I won't have to bother with PPPoE or login pages. Try requesting for the same thing, maybe you'll get a faster resolution.