I've exhausted every other avenue, so the next logical step is to post publicly here. This is getting incredibly frustrating.
As they say in "Pushing Daisies", the facts are these:
I have been a Primus customer since July 2002.
I am currently on a Primus ADSL1 DSLAM, on what I believe is a ULL (signed up as part of the "up to 8000" ADSL1 plan when I moved from dialup to ADSL back in December 2004). My service is bundled and home phone is also Primus of course.
Since about March last year I have been on a plan that's listed in my toolbox as "ADSL2+ Extreme 60Gb 12 month (2EX1-P)". I was placed onto this plan by a helpful former Primus employee and Whirlpool rep after posting that I thought it only fair that people on ADSL1 Primus DSLAMs should enjoy the same rates as those on ADSL2+ ones.
At the time of this happening, there were no available ADSL2+ ports in my exchange anyway. I don't know if there are now, and I don't especially care since I'm perfectly happy to stay with the connection I have, which is rock-stable, syncs at the full 8Mbps and anyway, I cannot afford the ridiculous downtime that would be required thanks to the churn-churn process required to move.
I currently pay $69.95 for my 60GB plan. The Big Kahuna plan would see me paying exactly the same for 200GB. Therefore I want to change plans. However, even after agreeing to a 2 year contract, sales staff cannot put me on that plan. Their systems tell them I am not able to be on it as I am an ADSL1 customer and that means Telstra-DSLAM plans only.
I've spent hours on the phone trying to speak to someone who can sort this out, all to no avail. Notes have been left on my account, people have been internally emailed and never replied, and I have been promised a call back to update me that never materialised. Last time I spoke to someone in sales, they transferred to to customer service, who ummed and ahh'd and put me on hold for 10 minutes, then typed a long email and told me to "call back in a week."
I've emailed the "wpenquiry@primustel" address to bring this to the attention of the usually-helpful Whirlpool reps. I sent that last Wednesday evening. No reply.
In desperation I messaged a Primus rep on Whirlpool to ask if he'd seen my wpenquiry email. He said he wasn't on that list but would chase things up for me. Last I heard from him was about 11.30am Friday: "OK, We're just chasing this up now. It's been escalated to our network guys, so I'm certainly hoping to get an answer for you by the end of today". I have messaged him twice since and heard nothing more in reply.
I'm beginning to get a little paranoid here! Is there someone at Primus going "whose enquiry is it? HIM? Dump it!"

All I want to do is change plans. While the original moving of me to the ADSL2+ plan apparently took some account tweaking - the rep who did it at the time recently said in reply to me asking, "if you just get a straight planchange done you should be right, if i remember rightly you were on an adsl1 port, i just forced you to a 2+ plan, the account should already be "sufficiently screwed" to just allow another planchange" - it surely must be possible. It's taken nearly a month of calling, messaging, emailing and chasing and I'm no closer to figuring out what's going on.
But please, I stress, whatever you do, DON'T set a churn to an ADSL2+ port in motion! I *cannot* be without the internet for weeks, or indeed even days at the moment.