Dishonest service provider

I am very disappointed with Cell C's dishonesty after 10 years of my loyalty , My contact expired in September 2020 and i decided to run it as a month to month contract as i did not need a new phone so i kept it for airtime only ,meaning i was paying R157.00 P/M. In May i got a debit order of over R250 which i rejected thinking its ***** as i have made a agreement at their Dainfern branch that i DO NOT want to go over my allocated airtime . I was charged a penalty fee of R70 for that failed debit order and was debited R300.11 in June 20th , This weekend i got an email that am in arrears with R157.00 but when i call the call centre they say R236 and charged a penalty fee again because CELL C failed to Debit the correct amount i owe them . Therefore if you guys failed yourselves why must i be punished your incompetence's ? I am willing to settle the R157.00 In arrears for May however if you will charge me the penalty fee of your your own errors i would like to have this contract CANCELLED !!!