Rain Incorrect Billing Issue

Rain has changed my data plan from "unlimited 4G 24/7" to "Pay as you go" at the beginning of June 2020. I stopped using their sim card as soon as I realized that my data plan changed, unfortunately at the time, I had already used up more or less 35 gigs and I wasn't aware that I was on Pay as you use(as I haven't authorized the change of data plan and no one notified me that my plan has changed) and as a result, my June month-end invoice was ZAR 1785, these are the line items from their invoice(usage) "unlimited 4G" 24/7 23.1790 GB 01/06/2020 - 04/06/2020 R55.54(excl VAT) and "Pay As You Use" 34.4314 GB 05/06/2020 - 30/06/2020 R1,497.24(excl VAT) - I am now required to pay for the period where I was on "Pay As You Use" even though I did not change my plan and is not my fault that the plan changed, and something to note is that rain takes on average 2 weeks to respond to queries, this is despite their poor network that keeps on dropping now and again and yet their website claim I should have no network issues as I am in the JHB CBD