Controlling internet use - bandwidth control

Hi All

We got a nice fibre optic line last month at the office, but on Monday the people called me, no internet. Calling Webafrica, I hear that they used every last bit of our data package in the first few weeks. All 300GB. Previously, on ADSL, our use were around 200GB per month. That included some torrents and stuff, but with the faster internet it seemed if people went crazy.

So, I would like to install some gateway or router that I can use to:
- Log all internet traffic (if possible, not critical)
- Limit the internet speeds to the different PCs (perhaps to 8kb /s - 20GB per month)
- Assign each user or IP a 20 GB data allocation.

I got a PC and installed Ubuntu server yesterday. The PC have 2 NICs, one facing the internal LAN and the other the external WAN. But, I have wasted now 2 days trying to get this working. I tried squid, tc and trickle, but after spending alot of time reading I am yet to get it working.

Can anyone perhaps tell me of a method, piece of equipment or person that can assist me with this.

Regards

Morne