We have an Ecommerce site with a monthly subscription. They have optional add-ons for additional functions, some free, and some paid for per month, which notifies you if they are paid for when you install them.
However, one of the free ad-ons we had installed has now been changed to $69/month, and we have been charged for the past 3 months. As far as I can tell we have no notification for this change, other than seeing it on the invoices just now.
What are our rights and regulations in this subscription based world?
You have no rights, you agree to pay them monthly for whatever services they are offering you at that time.
If you've been charged for something without being notified/agreeing, then you'd need to complain to the company about it before any potential escalation to the ACCC etc. But all you'll get is anything between nothing up to a refund of $207. If you want those features going forward then you'll succumb and agree to pay that figure going forward.
If you don't like the subscription then you are free to change providers. You did think about this when you first signed up, right? You didn't lock all you data and facilities inside a proprietary service with no way to cleanly export everything?