Autopage
Cancelled Contract and I am still expected to pay

I had cancelled my cellular contract with Autopage roundabout March/April 2012 and requested that the line be converted to prepaid. This was done at the Kenilworth branch (excellent service from that staff) of Autopage Cellular. For months I struggled to get this done effectively due to inefficiency at "head office" and it was eventually referred to Jay Chana at Legal Department. Eventually we made some headway and the line was converted and the account settled (I have proof which shows that Autopage owes me R50). Now, over a year later I received a LETTER OF FINAL DEMAND and I have been BLACKLISTED for non-payment. This for service I never requested or received? The last time I checked it was illegal to from people in South Africa.