Hi. If you are using a dual SIM phone, then you could be dialling from an incorrect one by mistake - please kindly double that. Otherwise, it may be necessary to contact Net1 (Zazoo Limited) support using any of the contact methods here for the best advise. One has reported to have recently used that service and that it all of a sudden quit working as you report. We referred here to support in the same manner as out support is sadly informational (and limited).