Pathetic service from Accounts Department

On 30 January 2016 I cancelled my Vodacom 1GB Tablet contract because my contract had expired. Noluvuyo Mgwangqa told me that my migration was successful and from 29 February my number will be on Prepaid, as I requested. Now all of a sudden I realized that my number was never moved to prepaid, as the My Vodacom App tells me that my account is standing on R2602.95!!!!!! And now Bulelani Skulu tells me this is due to out of bundle data rates? How is this possible when I'm supposed to be on Prepaid and not still on Postpaid??? I would like this error to be corrected ASAP! As I will not be paying this amount!