Around 20 gigs just disappearing from my monthly Vodacom allowance

Good day

I receive 50 gigs of data from Vodacom monthly but lately have seen that the amount of data it says I have used and the detailed data report are vastly different. I called the customer service and was returned some of my data. However in the detailed report it also says I am have used 16 gigs of download and on my download history file on my Mac you can see is less than 2 gigs for the same period. Then it also claims sharing files with others which I do not do as I work alone from home and do not share files with anyone. Then today I bought 10 gigs. I went on Skype for 22 minutes and then looked at my app and 3,5 gbs were gone from my 10 gigs. Nothing else downloaded during this time.

I have asked the call centre for a an investigation over the last several months as I have seen this occurring for some months now. But according to Vodacom I have used almost 70gigs in 3 weeks including 12 gigs in Facebook while I have been taking a break from Facebook.

This is ridiculous, that you take data from me in front of my eyes.

Pease can you investigate.