Tired of Cell C costing me money

I am so tired of Cell C and their incompetence to understand simple English. I've been having issues with them from last year May. Due to unforeseen circumstances my debit order went off unpaid. I did make plans for them to double debit my account at the end of June, however they continued to try and debit my account at different date causing my bank account to charge me unpaid fee's. this continued for months because they couldn't follow instructions. The amount of bank charges cell C costed me is ridiculous. Finally I managed to bring the account up to date. In December the account went unpaid again. They again tried debiting me on different dates without consulting me and caused bank charges again. I called them and advised to double debit but they still continue to do their own things. Cell C should be liable for all my unpaid bank charges due to their imcompetence.