No proof of contract!

I was with Virgin Mobile until the end of 2013. After major trouble to try and cancel my contract and resorting to Hellopeter, they now all of a sudden handed me over to debt collectors. Back in 2013 according to my own records my contract expired in December. When I phoned them to give notice of cancellation they told me that my contract only expire in October 2014. I then requested a copy of the contract and after another week I phoned them as there was no feedback. They told me that they didn't have a copy of the contract and will therefore cancel it and write off the handset. Of course it wasn't done. I then resorted to their head office and finally they told me that the contract will be cancelled within 30 days. As soon as I put the phone down all of a sudden my number did not exist anymore...contract cancelled and I never heard from them again. This week,out of the blue I receive a call telling me that I owe more than a R1 000! Without any statement or notification from them ever again. I emailed them on Monday and yet again no reply after I again requested a copy of the contract. I hope that this matter can be sorted out asap!