Data vanishing when hardly used.

I made a point of only using my wifi ****le from 5pm to 8:30 am Monday to Friday as I would have access to my wifi.

And like last month once again data I'd finished. There use to be 2 people using this wifi daily and ran out occasionally by the 27th.

Now one person is using it and 50 % of the time isn't using it, so how can 20 gigs of data just disappear.

I'm getting tired of paying you so much money every month. To have to run into this problem again.