Paying R250 per month for R1200 debt in 2011

In October 2011 I received notice that I owed R1200 to Virgin Mobile on a contract for a phone. The phone in question was ****** before I received this notice, and I had notified Virgin Mobile of this, however from January 2012 till now I have still been debited R250 every month. The debt has been fully paid a long time ago, and now Virgin Mobile owes me alot of money. Every time I try to contact Virgin Mobile I have to speak to a different person, and the issue never gets resolved.