You can also use wvdial
Install it using sudo apt-get install wvdial
Then, run sudo wvdialconf
And edit the config file sudo gedit /etc/wvdial.conf
You will get something like
[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = USB Modem
ISDN = 0
New PPPD = yes
Modem = /dev/ttyACM0
Phone = *91#
Username =
Password =
Baud = 460800
Enter the Username and Password if required (leave blank if it's not required) . Also provide the Phone number to dial. For eg: *91#,#777 ...etc
If the phone is connected using USB, the Modem value will most probably be /tty/USB0
or something similar.
Finally, use the wvdial command to initiate connection.