Landline phone through PC

[H.S.Rai]

I wanted to dial telephone number (not using any Internet, just
telephone network) and if possible attending phone through PC.

I have "conexant RD02 D400" [having only one port to connect phone
cable, and not second port to connect phone instrument], which is
connected to PC through USB port. I was able to use following command:

modem-cmd /dev/ttyACM0 ATDP123456

which rings bell on dialed number.

On picking remote phone, I expected that speaker and phone will be
used to communicate, but that did not happened.

Is it possible to use PC's mic, speaker or head set attached to PC? If
yes, which software or what setting?

-- 
H.S.Rai