Billing out-of-bundle rates for in-bundle data

I have a 5Gb pm data contract, which carries over data not used into the next month, for up to 3 months. But when I use any of this saved-up data, MTN bills me out-of-bundle rates.<br> <br> Despite explaining numerous times to the supplier via their normal support channels (call center as well as e-mail), their poorly trained staff keep telling me the same thing (specifically, that anything over the monthly 5Gb are out-of-bundle rates) - and not listening to the problem that they are billing me for saved-up IN-BUNDLE data.<br> <br> To the supplier: My ID Number is captured with this complaint - please use it to see the reference numbers related to my communications.