Migrating back to prepaid

Can someone please explain to me how does it work that I signed a 24 month contact with a store, but yet after the 24 months I still need to beg for my contract to be cancelled and for me to be migrated back to prepaid. I dont understand this, Now I was told someone will contact me within 3 working days to explain the process, which process exactly because my contract has ended as simple as that and I want to go back to prepaid. I was also shocked to hear that they would have continued debiting my account even after my contract has ended as long as I didn't ask them to cancel. LOL, this is a joke why call it a 24 month contract then, it should be called a life contract. I want to be migrated back to prepaid, my contract has ended thats simple