Call Of Duty Online Data Usage?

Okay, so every month we receive our internet bill stating we go over our monthly usage by, on average, 40GB/month. My parents constantly blame me for this as they don't see any other reason as to why we're going over.

Just to state: there are 4 computers in the house, used daily. 4 iPhones, 1 iPod touch, 1 iPad.
I play on average 1/1.5 hours per week night, and maybe 7 hours over the weekend (max.), so in total per week about 14.5 hours. I tend to host the lobbies on CoD Black Ops 2 (PS3), as I have the best internet.

Can my online playing be the soul reason to the internet allowance going over every month?
Or what other causes could there be?
We try to call to see what uses this data but we're not allowed to know due to the companies law or regulations…
If you can please state how much data my playing takes up (per hour), as it would be useful, here is some of my set up information which may / may not be useful:

I use a PS3 Slim, 160 GB, 1080p Television (no 3D), HDMI input to my television, I also use turtle beaches, my internet is plugged directly to the PS3, through the internet in the electricity lines.

We use a BT Home Hub which out puts a Wi-Fi network, it is also connected through the electricity using 200mbps plugs, which connects to an apple router to create a second Wi-Fi network, and another router to create one more Wi-Fi network (3 in total), and the last one is used for my PS3 direct plug in. All the computers work over Wi-Fi.

Thanks for answering, any answer is appreciated!
Max

Call of duty shouldn't do that i play alot like say 12 hours on the weekend and maybe an hour during the weeek but it doesn't affect it are you watching alot of netflix or youtube?

To give you some kind of clue. I use Mobile Dongle Broadband (a 15GB package) i rarely play Xbox Live, but when i do, it will use around 200MB to 600MB of usage in 1 to 7 hours when playing games like COD.

Some games use more usage, Forza Horizon really ZAPPED my usage and used about 600mb in a little over 1 hour. But playing games like COD, 1 to 7 hours will use roughly 200 to 600mb. So around a 1/4 or 1/2 of 1GB every 1 to 7 hours.