Cancel the contract that i didnt upgrade to

I have been with Cell c for more than 12 years now and i had a contract for data which they have been deducting R121 from my bank account which expired last month July. A lady called me two months back to upgrade and i turn down the upgrade. and notifying her that i would like to cancel the contract. today i receive an sms from cellc reminding me that my bill of R 345.99 is due month end for what servcie i dont know and in this econmy from 121 to 350 is crazy. i called in the customer service asked security questions passed and the gentleman told me the contract was not cancelled from their system and i have to call cancellation department i did got through a lady asked same security questions which i have answered and she said i have failed the security question and she cannot help.

Am so frustrated with Cell c as this is not the first time especially if you need go through the cancellation department, i understand they need to retained customers but not like this. i need that contract to be cancelled cause i didn't upgrade to whatsoever services that i was not even told what's that for. coz really 349. is like a cell phone contract not even data.

Cell C deducts from my bank account every month and i gave them the cell phone number the amount the use to deduct and my names , id and adress what more do they need from me.