Disappearing Data

Hi, I am having problems with DATA disappearing from my Vidacom data only sim card account. I have had to top up for the last few months even though I am sure I did not use all my data. So I ran a test by switching off my modem last night, the 1st Dec 23. I looked at my usage today, 2nd Dec using the Vodcom app. The total showed 24.18GB remaining of my 30Gb monthly allocations, ie 5.82Gb used. Hower the detailed usage showed only 532.8Mb used on the 1st Dec, which is definitely about right. About a factor of x10 wrong. So my account total is wrong and this is what I am billed on. What is going on? Unless this is fixed and it am defunded my topups, I will have to stop using Vodacom. Note. This is sent using MTN so as not to effect my Vodacom total's.