When we updated our pricing last time we updated our site, every page (including Seller Admin) had an alert bar at the top for many months, linking to an announcement which explained the pricing change among other site updates.
Our subscriptions work by helping you set up an auto-payment plan in your own PayPal account, telling them to send us the same amount every month. We have no way of billing/charging you from our end, nor can we alter the payment terms once you set that up, so it's up to each subscriber to change their own plan if they determine their usage needs would qualify for a different plan.
I see you also sent us an email about this, so we'll followup there once we sort out a resolution with our Billing manager for your particular situation.