Unauthorized service

My phone was ****** last year in July 2018. On the 28th November 2018 an account was opened with all my details. Loans potter SA is now billing me for R1780 and wanting to Blacklist me with Trans Union. I am unemployed and won't even be able to qualify for a loan never mind afford there service. To date I haven't received anything from them but I am getting billed for something I didn't apply for. After numerous attempts to sort this out with them I have been receiving letters of demand, court orders and Black Listing threats. How can I get this sorted out. They just debit my account without authorization and I have had to return the debit orders as I have not given them permission or need them for anything. Please can someone help me with this issue.