TELKOM does it again!!!

Absolutely livid right now. Had a Telkom account which I cancelled on 13 Feb 2017. NOW 2 years later it pops up on my credit report that I owe R277.41 for an invoice dated 26 April 2017 (2 months after I cancelled) Spoke to Siwe at Telkom customer care and she told me there is nothing she can do, there is also not a Manager on duty... So how am I suppose to resolve this?