Can you define 'studio immersion heater' a little more ?
Is it just a normal electric hot water service with an element ?
Or a smaller version of those ?
I googled immersion heater, but don't think you have what comes up !
Also, "This is due to the fact that the smart meter only allows power to my studio immersion heater 2 days a week, Saturday and Sunday from about 5Am to 3pm."
You don't define where you are (all states seem to have their quirky tariffs / availability of options etc) but I am sure no plan / tariff would have such timing normally.
Hopefully an AGL rep here can take you up on a private message and sort this out.
I can't work out why you haven't gone to AGL via phone or website chat, it's really not too difficult to do.