Unhappy customer

My Mr Price account is handed to them and I've made an arrangement with one of their consultant on August to deduct the money on September from my bank account, yes they did deduct the remaining amount that I owed Mr price on the date we agreed on but the problem now they say they didn't receive the payment, how I don't know because I even have a proof of payment. I've been calling them since September until now to resolve the issue because Mr price is it sending text about the outstanding balance, I'm still not getting any feedback from them Can I get a serious help because this is affecting my credit score