COMPLAIN ABOUT MTN CELL PHONE CONTRACT

I am unhappy with the service I got from MTN. I had a cellphone contract with MTN which gave me 2GB + 20 Minutes. My contract expired on the 31st of May 2024 and when I would open my MTN app I could see that I am still being billed for the month of June. I went to my nearest MTN store today to enquire why I am still being billed if my contract has expired/ended. They told me that I have to cancel it otherwise it will be on a month to month basis. I immediately told them to cancel it as I have finished my 2years as on the contract. After my contract was canceled mtn immediately took all my data even the one I dont receive from the cellphone contract, I receive 30GB every month from my school (UNISA) which I had not even used yet and MTN took all of it. I am in disbelief as to why they would take my 30GB because it was not from my cellphone contract, my contract gave me 2GB + 20minutes but once my contract was canceled it took that and my 30GB from school as well. When I went back to the store they said they don't know why it happend and made me call customer car but they still also couldn't help me saying they can no longer see the information of my phone since my contract was canceled. All of my school data is gone and no one can help me get it back not even customer car, now I have to see that I make a plan for this month so that I can do my school work while my school made sure to provide me with the data needed but MTN decided it's theirs to keep. Please help Peter!