Cancelled contract but still being billed

I cancelled my 24 month contract with Vodacom during October 2015 since the 24 month contract expired on the 31/12/2015. I clearly indicated on the form that I do not want any of there services anymore, I filled in a cancellation form and I was provided with proof that all services will be cancelled effective from the 31/12/2015.<br> <br> I have received a bill from Vodacom dated 31/01/2016 for R104.99 for :<br> - airtime subscription R54.99<br> - 24 months Handset instalment R50<br> <br> I do not want this service - who authorised this services???? I was never informed about these services.<br> <br> Reverse these charges and since this contract has already terminated on the 31/12/2015 - I do not want ANY services with Vodacom, my contract with you has already expired.<br> <br> <br>