I tried this steps in Ubuntu OS from My Sony Ericsson K510i. I am using Airtel Subscriber.
Hope it will work in other Linux distros also.
Start your pc and now enter id root and password (you must be knowing that!) Now open terminal and type "dmesg" It will detect all the device connected with your pc including your (usb, serial ) data cable.and it will display log in the same terminal read that log carefully now check which port has been detected by it. It detected ttyUSB1 on my pc.
it will detect ur mobile and it will write the value on wvdial.conf file in etc directory.
Now open the file /etc/wvdial.conf from your terminal,
In that file, you can show a existing configuration. You just remove all the lines and paste the following code.
#Paste the following lines to your wvdial.conf file
Modem = /dev/ttyUSB1 #note1
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
stupid mode = 1
Modem Type = Analog Modem
Phone = *99# #Note2
ISDN = 0
Username = a
Password = b
Baud = 115200
#Note1: May be varied depends upon your hardware config.
#Note2: First check your mobile phone dial No.
step 3 Open the file, /etc/resolv.conf and enter following lines. Now dont delete the existing lines. You just append.
service named start
Now log out and log in as User and open terminal now type su - and press enter, than type root password for your super user mode.
Then type wvdial R in your terminal
Hope now you are connected to Internet now enjoy surfing . If u want to disconnect than just press CTRL + C or killall pppd
And it will disconnect active connection!.