Massively overcharged due to usage meter being wrong.

Hi. We got our bill for November that says we used 4 terabytes of data and are being charged an extra €200. 

I've reviewed all of our usage and this cannot be possible. There's no way we used that amount, I remember checking the usage last month and it was only on about 400gb towards the end of the month. 

Whats even worse, less than 1 week into December it's already telling us we've used over 11TB! once again. I don't even know how this is possible.
We simply cannot afford to pay this amount. We've so far for the past week been unable to get through to customer support on the phone so trying this as a last resort.

This is the second time we've gotten overcharged like this. 

Looking at our usage meter for November, it says we used over 1TB on the 17th alone, and then another spike of just under 1TB on the 30th.

Both of these days we were all at work, so I really don't know how its possible that we used this amount in the space of a couple hours. 

For the month of December how in the name of God is it possible that we've used over 11TB already?



Could you please help us out here as we simply do not have the free time to be waiting on hold? 
Thanks.