Disappearing data

Let me start off by saying I fully understand that Mondo is only a reseller for Telkom, but I wish somehow you could stop working with them as your image will be tarnished by your partnership with them, they are by far the worst service provider ever, I took up a 10GB contract through Mondo and so far everything was good until this month, well my usage for this month was abnormally high, to which I decided to let it slide as maybe I might have over used my data, but something just didn't add up but I kept quiet, I checked my balance around the 15th and I was left with about 1.9GB,whicj is inpossible but I thought ag let me let it go, maybe just maybe it could be an error from my side and I decided to put the router away and use my normal data which I get from Vodacom, so I did that knowing I have 1.9GB on my telkom account, so today I decided to use my router and it tells me I'm out of data....how?? When my router was off since the 15th?? I live alone so no one has access to it...a whole 10GB gone just like that? And Telkom won't even give an explanation....how do I get out of this contract without any penalties? I honestly cannot be paying for data that just disappears, please assist with that...time to switch service providers this is not on