saurubh,
i am also using the lg 340 phone with a serial cable which i bought from bazee for 150 bucks on my laptop. Basically you have to install the software from reliance which in addition to the dialling softwrae also installs the modem drivers for your phone. then rboot with the phone connected to the serial port,, go to dial up networking and choose a new connection with modem selection as 19200 bps standard modem which is actually your phone , user name and password is your phone no with std code incl the zero. number to be dialled is hash 777. please try and let me know. you can also use the r connect dialler if you want