Vodacom ****** me data again

Yesterday I borrowed 100 megabytes and I used dat data on whatsapp then I went to sleep around 22:13 and I switched off my data. At 3:28 am today I received a SMS saying I ran out of data then I immediately called Vodacom customer care centre and I was assisted by Tebogo who refused to give me his sure name. I told him my query and he checked on the system and he confirmed that on the system it's showing that at 22:13 I had 99 megabytes and its not showing anything on today's date. My complain is that how come I run out of data while my data was switched off? And now I have to pay for a data that I didn't use. I even checked the data usage at first it said I used 48. Something mega bytes yesterday and 0 megabytes today, when I check later it said I used 50 something megabytes yesterday and 0 megabytes today. So where did my data disappear?