Data

I was transferred 1gb of data at around 23:59, mind u I was sleeping and my data was switched off, woke up at around 9:30 and switched on my data but only went to my emails, to my surprise my 1gb gone hw cuz I didn’t open any App only had emails, how because can they please explain cuz I already have another case going and still with no answers. Vodacom is not reliable and this time am really tired to a point that I want to cancel my contract with them, I have heard it with u guys really