Recurring Data Issues

I am fed up with having to call Vodacom every month and enquire why my data bundles, that were assured by the consultant at the time of inception, that the balance was to be carried over to the following month up to a maximum of 2 months. Why can't this just be rectified and alleviate my frustration of holding for at least 45mins every month to get the same answers, \we don't know why