M1306B gprs communication please help!

hi!
i am trying to set up gprs communication between two wavecom fastrack M1306B modems, connected to the serial ports of two computers, using ONLY At commands

i have some difficulties
i am useing the following commands
at+cdgcont=1,“IP”, “internet”
->responce: OK, (internet is the apn of my service provider)
at+cgatt=1
->responce: OK
at+cgact=1,1
->responce: OK
at+cgpaddr=1
->responce: OK, it shows my ip address also
at+cgdata=1
->responce: NO CARRIER

could you please help me, i probobly should be using ppp protocol, but i do not know how to connect to a specific ip address,

can sombody also explain how the data transmissino takes place? (ports, atcommands, i could’nt find anything about this in the at command set)

THANK YOU VERY MUCH!!!