Cell C should just pay me back my money they owe me, and take of R322 On credit berau

I took a contact out with Cell c couple years ago, i did over paid them to date they did not reemburst me, the last chat they had with me is that they want me to send them a private message, but they dont provide an email addrress. I am still waiting for them to come back to me my credit report shows that i owe them R322 I dont know why they did put that on my credit report cause i dont owe them penny they owe me