What qualifies as grounds for suing for harassment?

For over two years now I am getting harassed by MTN via debt collectors for an account I know nothing about. I submitted anti-***** documents and still! Even the information the debt collectors have doesn’t match my profile to show that this is *******ion. MTN at Northgate Mall are also not processing the anti ***** claim correctly. What qualifies as grounds for suing for harassment?

Case number: BA***