Data

I complained as I took out a Data contract in the middle of the month.and when my data dissappears within 2 hours I was told its calculated based on pro-rata,they then load 1gig that lasted until the 12th this month as on the 1st in the morning i had 400 Mb from their 1gig that was loaded previous month and on the 10th I had 318Mb I only use this Data for my emails on my Notebook then on the 12th my data was gone and when I call vodacom to ask about the 1gig that I subscribed for I was told it got finished on the 11th not the 12th.my Question is how can it not show when I check my balance as on the 1st I only had 400Mb what really happened to my 1Gig.