Rain Charging me For Data I have not used after I stopped using their service!!

Terrible service, joined rain a couple of years back when I was a first year student at University, after completing my studies I stopped using rain as I was unemployed and had no means to keep affording the service so I stopped using rain. To my surprise I am getting a call recently from credit collectors forcing me to pay R1300 for data I have not even used ( I estimating they’re charging me for 5 months after I stoped using their service, and mind you my part of using Rain as a student was that it was ‘Pay as you go’, so why I am being charged for data that evidently I have not been using is appalling and paints rain as a ****. I am dissapointed at how some big companies conduct their businesses. Wolves.