OPC (Online Phonebill Calculator) If you connect to the internet using a modem (or any form of dial-up connection) then OPC is the ideal tool to monitor your phonebill costs due to internet calls. It does everything from generating ... Cost: $15 Buy full version       Trial version       Publisher: UKULI Software     Descriptions OPC (Online Phonebill Calculator): If you connect to the internet using a modem (or any form of dial-up connection) then OPC is the ideal tool to monitor your phonebill costs due to internet calls. It does everything from generating charts/reports/logs to automatically timing connections.