Data contract billed for calls i did not make.

I had a 2 year contract which ended on 03/14. In April they called me to renew my data contract at a cheaper rate of R99 pm from R143pm which I agreed to. To my horror I was bill in over R2900 in April 2014. I reversed the debit order and complained at an outlet in Bronkhorstspruit. I was told my account reflect with a name of a white male. I pursued the matter with Accounts @ Head Office n I have the following reference numbers: *** I was told my previous cell number was deactivated and a new one was activated in April 2014 with the following cell number *** the old cell number for which I had a sim was ***. *** Daylan assured me that he has closed the new cell no. on 15/05/14 on 2/06/2014 ref no.: 380542 Gideon promised to have someone calling me back but no one did. I was eventually handed over to lawyer whom I explain the situation to and they did not pursue the matter further. I have recently received a letter of demand for R6141.41 from different lawyer. I feel I am being bul**** and need your assistance urgently. I have also contacted icasa on this matter today. I feel this is a breach of the NCA by Autopage as I didn't sign for a caller deal.