Every one at Cell is Lazy and Blind

Cell C have since last year kept on send me a statement that I need to pay them R231.25. I have paid an amount of R232.00 on 29/07/2017. I have also send them proof of the payment and my bank statement showing that this has been paid. The have asked a company by the name of NuDebt also to assist them and I have send them the info as well. I am promised every time that someone will come back to me and no one has. I have asked for a manager from both companies to contact me and no one has. They keep asking me to pay this and no one seem to do there job. I am SICK of this now.