IP Phone with Timer and Toll Indicator

I’m planning to setup a walk-in VoIP Calling Center using IP Phones in booths with a centralized accounting system. I require IP Phones with an LCD display that has a call timer plus the running toll to be paid. I know this has to run in combination with a billing software. This way the caller doesn’t have to guess how much he will pay for the call since the actual amount due is always displayed. I saw a calling center in Rome,Italy using these kinds of phones but wasn’t able to check out the brand. Can anyone help?