Assuming you have a Vodafone GPRS PCMCIA card, all you need is to create /etc/ppp/chatdata:
'ABORT' 'BUSY' 'ABORT' 'ERROR' 'ABORT' 'NO CARRIER' 'ABORT' 'NO DIALTONE' 'ABORT' 'Invalid Login' 'ABORT' 'Login incorrect' '' 'ATZ' 'OK' 'AT+CGDCONT=1' 'OK' 'AT+CGDCONT=1,,"Internet"' 'OK' 'ATD*99***1#' 'CONNECT'
Then use this to connect:
pppd connect 'chat -v -f /etc/ppp/chatdata' /dev/ttyS3 115200 crtscts modem noipdefault defaultroute user web