Cell C it’s a ******* company

Hi there, would you kindly help me, my name is Kgaugelo Ma*****e i had a cell phone contract with cell c my contract ended in July 2019 so they kept on giving me airtime and deducting the money from my account, i contacted them and they told me i need to call them and tell them i want them to stop the contract, i did phone them and they told me to pay the money i was owing which is the money for the airtime they’ve been sending me, i paid the money and phoned them again to let them know that i have paid the money i was owing and i asked them not to send me the airtime anymore and they must change my line from being contract to prepaid and they did that, they sent me a message to tell me my contract has been canceled my number is now a prepaid,i was so happy about that especially that I’ve been going up and down with them phoning them to stop my contract and they kept on deducting the money,guess what..they actually didn’t stop sending me the airtime after I’ve phoned them and even spoke to one of their managers and they promised to stop it so now they telling me i am owing them +-450 for the airtime they kept on giving me after i told them I’m no longer interested,so now they cut my line i can’t make calls i don’t know what to do i am no longer working I’m so much stressed i regret the day i signed the contract with cell c they are such a ******* company they only thinking for their pockets i know they are getting commission on the airtime they are selling but they should get in a right way not by forcing or ripping their customers, hellopeter please help me resolve this matter.