cancelling a call limit without customer approval

+/-20 months ago I went to Vodacom Customer care at Vodaworld Midrand to request that a call limit be installed on my line. It has been working just fine since. However my statement received earlier this month shows an overspend for data consumption totalling R576 ( R226 and R350 a couple of days apart ). Upon calling customer care on 082111 I am told that the call limit is reflected on the system but has never been activated. This is a blatant lie as it worked just fine before and I was there myself facing the consultant when this call limit was requested and implemented. It looks to me someone at vodacom deactivated the call limit purposefully without my consent out of greed or incompetence. The cherry on the cake is the customer care consultant tells me laughingly over the phone there is no way I could get out of paying this.