Poor service incorrect deduction

I had a contract with Vodacom top up R300 I asked for a premature cancellation on the 6th of February and paid the full amount on the premature cancellation quotation on the 9th of February which I have proof of my number then went over to pre paid I called their call centre and spoke to a few of the consultants with no joy then I spoke to a Justice who would not allow me to speak to a supervisor Vodacoma billed me again on the 25th Feb for a number that is on pre paid they dont want to reimburse me.