Data Vanished

This morning I logged into the internet at 07:58 to 09:00 and afterwards I checked my data balance it was 623MB which I have an sms from telkom to prove it, I logged in again now for 15 minutes and I received notification that I have ran out of data. Shocked and surprised I called customer service with case number ***9 and the lady I spoke to told me inbetween 07:58 and 09:15 I used 2Gig of data. How can I use 2Gig of data when my balance is 623MB? I'm disgusted because she cannot explain how my data has vanished but told me to wait for 7 days I will receive a call from their technical department, 7 days? No I do not have 7 days to waste its either someone calls me and tells me what happened to my data,my data is refunded or I simply change to another service provider because this people are *******