Vodacom data missing

I have been a Vodacom client for as long as I can remember, had my 1st contract with Vodacom in 2017, did my upgrade in June and this month is literally the 1st month I’ve run out of data twice in one month. How is it possible that it’s half way through the month and I’ve already had to purchase data twice. What frustrates me the most is that that when I called Vodacom customer care, all they could do is speculate it terms of how my data got depleted without thorough investigation. I know I’ve previously called in a couple of years back and asked them to block all subscriptions but this is honestly unacceptable. I’m at work from 9-5 connected to the work wifi and also have a separate sim for WiFi purposes. How is it possible for a person always connected to wifi to have their data depleted half way through the month.