Hand over of an outstanding amount?

I have had an account with Vodacom for many years. Easy 6-8 months back I changed from contract to prepaid - Therefore I no longer have an account with Vodacom and purchase my airtime when needed.<br> I have recently received an sms from Vodacom stating that they have handed me over for an outstanding amount of R2382.04. Two days later I receive a call from a collections company named Nimble wanting to know when and how am I going to pay this outstanding amount. Now I am very confused because Vodacom will not move you from a contract to prepaid unless your account is sitting on a nil balance. <br> I have requested for the invoices to be mailed through as this is news to me. Nothing has come through to date. How many more times do I need to plaster Vodacom on Hellopeter before they get their act together with regards to their accounts department. I have not had any success from them with regards to sorting this problem out and wonder if it is not a question of now taking it to the media- would that help!!!!! The reference given by Nimble collections is BTV37254. <br> This is shocking service from Vodacom