I wonder if they have not made changes on their side recently? You are not the first person to say that it gets rounded to MB, but my current balance always have decimal values, so they do not seem to round to the nearest MB
I don't know, but I did that test just a couple of days ago, and it is 100% definitely rounding up as a matter of fact. Maybe different packages are billed differently? Mine is the 5GB/mo once-off up-front with black dongle. Plug it into the USB and try it in Windows. I suspect it will behave the same. You can see in Windows exactly how many bytes have been transferred in the session by going to the connection 'Status' dialog. I confirmed in each case that for each of those sessions I used at most a few thousand bytes, over literally a few seconds. So over three sessions of only a few thousand bytes each, right after one another, 3MB had come off the balance, even though I confirmed for 100% fact I'd only used a total of maybe 10 or 20 thousand bytes. Those MB never came back. It thus simply CANNOT be the case that the balance was declining in decimal MB amounts between sessions, EVEN IF the reported balance is rounded.
I doubt, if you are using a router, the connection should stay connected all the time (unless something goes wrong somewhere).
No no, listen to me. Lots of people have been reporting 'frequent disconnects' lately with Cell C (e.g. they can't be online more than a minute then get kicked off, over and over, seemingly mostly during peak times) (see this thread:
http://mybroadband.co.za/vb/showthread.php/298583). With the Windows-based software by default if you get disconnected, you have to manually reconnect, so it won't cause major bandwidth inflation problems. The disconnects are caused by problems with the Cell C network - NO router can prevent that happening, it's technologically impossible, it would have to be a magic router, since the problems are Cell C side. If your dongle is plugged into a 3G router, and the Cell C network causes the dongle to disconnect, the session will be over. Most routers are usually configured by default to auto-reconnect on disconnect from the network side, because the router's purpose is to sit on the LAN/Wifi and provide local connectivity to everyone using the router. Thus if the router is set to auto-reconnect, and Cell C kicks the dongle off every minute or so for (say) an hour, you will have 60 reconnects. During each of these sessions, Skype will use a few thousand bytes or so, and Cell C will then round each of these up to 1MB, eating 60MB of the balance in that one hour. If your router logs reconnects, you should be able to confirm if this has been happening. (Please, read closely what I'm saying, I AM one of the more "experienced guys" on the forum, I have worked with networks on a technical level for over a decade, I'm not just spouting random nonsense, you don't seem to be reading what I'm writing, you just gloss over and assume I'm not saying anything useful.) Log into your router's admin interface and see if you can find disconnect or error logs of some sort.
(*Edit* here is an example of the sort of thing I am trying to explain to you:
http://wl500g.info/showpost.php?p=186299&postcount=3 ... there is a user getting quite frequent disconnects of a Huawei dongle on a 3G router, and looking at the logs to show the disconnects and session times ... combine the abovementioned 'test' of mine with Cell C's "frequent disconnections" problem and you could quite feasibly have your 'data inflation' problem explained right there. *Edit2* To eat 700MB like this, you would only need an average of 23 disconnects a day over the course of a month. That many reconnects is not unthinkable even if you simply have poor reception, and not even factoring in the Cell C's network problems side of things. Since the latter are mostly peak time things, it could happen when you're not even at your computer, you could have 10 or 20 just between say 3 and 7 PM (which is when I had most 'frequent disconnect' problems)).