How to use 3G usb modem to make calls from Computer?

I have TATA docomo SIM and I use it to surf internet but I would love to receive call also while I am using internet. Currently I have to insert SIM in phone to make calls. What if I can make calls using my PC only.. that would great.. but I am not able to find way to do tht. I have micromax 3G usb modem.

Modem can send and receive sms but there is no option to make calls. if any one knows how to make call using this 3G modem through PC then I will be highly obliged.

Thank you sir.