Cell C ****med me

I am completely unhappy with Cell C and the manner in which they use their systems. I upgraded my contract in December 2019. It was a wifi router and a handset. i paid them up in January this year and I could not call in to cancel the contract when it expired. They continued to debit my account and when I finally tried to call I struggled to go through their system because 1) their security checking system doesn't allow a room for error in the details. 2) Whenever I was put through to their cancellations department the phone would cut and I would have to call again. Today I finally got through to cancellations and they could access my profile. Apparently I am paying for 4 contracts (two being the ones i upgraded with in 2019 and the other two being the other two that i was upgrading on. The person that was assisting me then apparently put in a line next to the other two contracts as if I was adding a new contract and not upgrading. Now I am told that I am in arrears and for the recently active contract the last debit is at teh end of July. Two things i need answers on: What does it mean to upgrade a contract, why was my initial contract not deactivated when I called in for an upgrade? Why do I need to continue paying for this recently expired contract until the end of July?

In my view Cell C owes me for the contract they kept alive after I upgraded to a new contract. I need answers.