We also have the same problem in our home... it has even gone over when we were gone for two weeks on vacation with all our equipment off and our consoles auto update features turned off. The technician went through every scenario with me and couldn't figure out why it went over when we weren't even home but also had no resolution for me other than to pay them an extra $30 or $50.
I've called Cox multiple times and all the reps seem to be trained to say "But only 2% of our customers are going over their data cap" ... ok so you need to start price gouging your entire customer base because 2% of them are going over their plan prob at most 50% or so occasionally throughout the year?
I asked why 2% overage is such a burden that we need to be charged extra for it and was told that it puts a HUGE strain on their equipment with all that extra bandwidth going back and forth... so you're telling me that extra money from your customers somehow magically relieves the strain on your network/hardware? Uh uh...
And I love how right on the home page Cox lists their stance on Net Neutrality:
"Details
Cox is committed to an open Internet experience for our customers. This means the following:
•No blocking of legal content
•No throttling
•No unfair discrimination
•Transparency in our customer practices
We stand by an open Internet because it’s good for our business, and our customers expect and deserve it."
But if you talk to a technician, they will tell you that Cox does NOT count any bandwidth that is accrued through the usage of their own branded Services. If you use Contour App to stream for example. Guess what... they don't penalize you for it. Sounds like the OPPOSITE of the above statement to me.