Cell C charging unpaid debit order fee like banks

I went to Cell C store in Brits Mall to ask why my data contract monthly installment has changed for the month of September and they told me that I was being charged a penalty of an unpaid debit order of January. I asked how do you charge a penalty of something that happened in January eight months later. My bank charges me unpaid debit order fee immediately so why are they also charging me . I went to Nedbank to deposit funds because I was told their debit orders do not run on Sundays. My line was never stopped, So what they charging me for? They can't just charge me R70 for something that happened in January. They also said I can complain as they dnt have a complaint centre.