Incorrect balance

I had a R 1 account with Edgars that I used to use to get discounts when I bought merchandise in the store and I also had a cellphone insurance. The cellphone insurance was paid from my salary and when I claimed for a cellphone loss I cancelled the insurance. I have received numerous communication from nimble advising me that I owe them and everytime I tell them I don't owe them. Can I get this sorted ASAP as it is affecting my credit record