Horrible Lack of Customer Service!!!

This has been the worst most horrible communication I have ever had with a company. Contacting me to say I have an outstanding amount on a cell c account and now it is affecting my credit score. I haven't had a cell c account in 5 years. I am willing to work with them and pay this if they could provide proof that it was in fact my account from 5 years ago. Sending threatening emails to take further action. I have repeatedly sent them more than 15 emails and they just say they will look into it. I cannot believe that a company is refusing to provide me with evidence of my account if I am willing to pay and sort this out. How is this company still operating if this is the type of service. Horrible horrible lack of service!!!!!! You should be ashamed that you can actually call yourself a company!!!!