I too am having random arbitrary multiples of 100MB being charged to my data usage. It hurts especially as I am paying $10 per GB for these extra charges. I run two laptops, one on XP and one on Windows 10, no Macs, keep them pretty clean, but even when not connecting get these 100MB charges
I have installed a network use tracker. Thanks for the suggestion on that. I am getting at least one 100MB download per day so should have evidence fairly quickly to either identify the source or identify a discrepancy from Optus. I tried the online chat and the lady tried to transfer me to technical team but it failed as they were all busy apperently.
Okay ! year on and we have had no joy I think it's time to, I have been on to Tech dept and they said they would reset, cool I thought problem could be solved ......please don't use your pc for 4 hours while we do this she said,okay I said,next day I switch on and I have used 377mb while I am offline ? when I tried to check on phone I get someone who knows bugger all about anything !!!! I hang on for 35 mins and thought it hung up and now will change to someone who gives customer service the way it should be Australia we are being dudded by Clayton providers:smileyfrustrated
I can confirm we only charge for data used while connected to our Network - more than happy to have a look into this further for you if you have any fault reference numbers handy.
Currently dealing with this myself right now, too. Years and years of never going over the (meagre) limit of data at my mum's house and then two months ago she got moved to a new plan and all of a sudden we've had two months in a row of excessive data gouging. Nothing has changed in our internet surfing habits and yet suddenly we're using a gig a day (sometimes up to 3 gig - and there's no way we're downloading 3gig worth of data a day on the speeds we have). It's currently being investigated and we're just scared Optus are going to say "well, you're stupid and you downloaded too much stuff" when we've never had a problem ever before and they'd know this looking back at our usage history. Apparently 2.9gig for TWITTER over a month. No way. And since making the complaint three days ago it's gone up a gig a day and charged us $10 for each new gig of data. Like, do they think we'd be stupid enough to not just go on a new plan if we were really using that much data as opposed to just spending $350 on a bill each month?