Telkom Wifi / data dissappearing.

I have a 20GB+20GB Broadband WiFi Router. I have never had any problems with usage or data depleting. This month ALL of the data dissappeared on the same day - mobile (which has NEVER been used), Nornal day usage as well as all of the night usage dissappeared. I loaded another 10+10GB for the last 3 days before the new month, and again everything dissappeared. I have logged a fault which hasn't been resolved.