Cannot load data bundles

Cell c won't allow me data after my data bundle has been depleted on several occasions now even when trying to load data before the bundle is depleted Cell C can not load the bundle in time or just informs you the transaction could not be completed why when my airtime is finished everything stops.<br> <br> As a result, I cannot load data bundles, and am forced to use out of bundle rates, which depletes my airtime too quickly. I would like this rectified