Disable internet only.

[UKBITS]

Hi All,
I need to disable internet access for a customer on about 50 Trinity XDAs but keep data open.
The XDAs are used to report back to a server with certain data, but the internet access is being abused by some of their employees.
I have spoken to O2 to ask if they can block port 80, but they tell me it's all or nothing.
Does anyone have any ideas on how to do this on the XDAs or any third party software to password protect IE?

Many thanks.

[UKBITS]

Since posting the previous question, the goalposts have moved.
Is there any way of having a windows style login on an XDA so when different users are logged into the device, there is a record of which user was logged in and at what times?
I know this sounds a little complicated, but there will be around a dozen users in this scenario and my customer's preference is to try to monitor who was using the XDA at a given time when checking the bills - both for phone calls and internet usage.

Thanks again!