Receiving an invoice for a prepaid service

Good Day,<br> <br> On 13/02/2015, I telephonically requested my blackberry cellular phone contract to be converted to prepaid when the contract expires on the 09/ March 2015. Contact person was Kevin Math?, the call ref no. ***. He informed me that I will be billed until the 31/03/2015 and I have free minutes which should be use before the migration. I received sms from indicating that I have to used up the free minute and the insurance will also be stopped on 31/03/2015. The service was disconnected on 31/03/2015. Purchased a voucher of R100 at Reds Mall, Centurion for BIS &amp