DATA DISAPPEARING

Good day, i receive every month my Telkom data on the 1st, 60 gig day and 60 gig night, Sunday the 13th at 20h00 I checked the data balance I had 16 gig left from the previous month and 60 gig left from the day time data and 45 gig night surfer. when i checked this morning the 16 gig were depleted and 60 gig day time data were only 12 gig. how the **** can the data just disappear like that. I've been trying whole morning to get hold of Telkom but can't get through to them please help.