exceptionally rude representative and failure of management to respond to numerous requests to address complaint

Shocking and aggressive service I.R.O third party claim. representative of company was rude and threatening - i.e sent me a rude threatening e-sms demanding payment or threatening to sue.When I approached the company and asked to speak to a manager, owner, director, someone higher up, the staff taking calls kept on blocking me by putting me on hold. when i after the third or fourth attempt spoke to a customer liaison officer, i was told i would receive a call from director to discuss my claim. i waited three days and nothing. when i called back again, the original representative coincidentally answered and i again requested access to management, and representative was rude and dismissive