Unexplained Data Increase

I have the EXACT same problem. Our past daily use was 3GB to 17GB. In the last month my daily usage has been up to over 100-200 GB. And on some of these days we aren't even home! When I called they told me to pay the extra $50 to get more GB. Other than that they couldn't help me. We have done nothing different in our house so I thought someone hacked into my wifi so I changed the password. I connected just my computer with 2 devices and I had the same data usage the problem the next day. I scanned my computer for viruses and there's nothing. So I'm frustrated at this point because there is no reason I used 100GB on a day when I was gone with just a computer that was in sleep mode. I'm wondering if it could be an equipment problem. Did you find out what your problem was?