Seeed Cellular Radio Voice dialing with Gadgeteer boards?

Has anyone been able to place a voice call with the Seeed Cellular Radio using any Gadgeteer board? For example using the following line of code: cellularRadio.SendATCommand(“ATD+1555999000;”); The Seeed Cellular Radio works very well for me sending/receiving SMS messages, much less reliable for GPRS communication over the internet, and now I need to verify its voice dialing capabilities. Thanks!