Technicolor TG582n Security Issue?

[#1]

Hi there,

I've got a Technicolor TG582n. The problem I am facing is, that my bandwidth is quickly finishing. (60GB per month). And now it's finished, the internet is really slow. I'm wondering if it could the router? Someone from outside my house is using my internet? I've changed the wireless password at least 2 times. With the Technicolor TG582n it shows which PCs are connected it gives all the details, I've noticed that couple of the mac-address are not any of my devices. ( I have a word document with all mac-addresses of my devices).
We have 6 people in our family, Myself, dad, mum, brother and two sisters. We barely watch videos only (20 minutes videos).  We download at midnight, So we don't use finish the bandwidth. Gaming wise, I barely play games.
This is the Usage.

[#2]

The obvious answer is to upgrade to unlimited which shouldn't cost anymore
Can you post the mac addresses you don't recognise and somebody here may recognise the item type/supplier

[#3]

Or copy and paste it in here http://www.coffer.com/mac_find/ to narrow things down a bit.

[#4]

You can block mac addresses from WiFi access using 'Home Network'. 

[#5]

For a DIY solution to MAC Address identification I used this