Telkom - Irregular data bundle depletion

Telkom chowed 5 gigs my data bundles a few hours after I bought 10 gigs. Even over the weekend, I was left with 5 gig then suddenly on sunday I was left with 2 gig then on Monday my data got depleted. On Wednesday morning around 4:45 am I decided to buy 10 gig but to my surprise at 12pm of the same day I got an SMS saying that I am left only 5 gigs of data. Where on earth did my data go so quickly? This is unusual and strange. I called the call centre and the case number they gave me is ***0