Heres some tips on how i got my Nokia n93i to allow me to borrow it's GPRS internet connection via Three Australia.

Using my debian/lenny linux laptop on 2.6.24

1. Setup your rfcomm bluetooth interface

This is my /etc/bluetooth/rfcomm.conf file (also attached)
Replace your device mac address with which ever is the device address of your mobile phone..

# hcitool scan
Scanning ...
        00:xx:xx:xx:xx:xx       dgtlmoon

So in your rfcomm.conf put this..

rfcomm0 {
        # Automatically bind the device at startup
        bind yes;

        # Bluetooth address of the device
        device 00:xx:xx:xx:xx:xx;

        # RFCOMM channel for the connection
        channel 1;

        # Description of the connection
        comment "PPPD connect";
}

Create the PPPD scripts

in /etc/ppp/peers/bluetoothconf

debug
noauth
connect "/usr/sbin/chat -v -f /etc/chatscripts/bluetoothconn"
usepeerdns
/dev/rfcomm0 115200
defaultroute
crtscts
lcp-echo-failure 0

and your /etc/chatscripts/bluetoothconn should look like this..

TIMEOUT 35
ECHO    ON
ABORT   'nBUSYr'
ABORT   'nERRORr'
ABORT   'nNO ANSWERr'
ABORT   'nNO CARRIERr'
ABORT   'nNO DIALTONEr'
ABORT   'nRINGINGrnrnRINGINGr'
''      rAT
OK      'AT+CGDCONT=,,"3netaccess";'
OK      ATD*99***1#
}      ""

the 3netaccess is some kind of packet-interface filter name, you can find this out by going to Tools -> Settings -> Connection -> Access Points -> Mobile Internet and putting in what is set for "Access point name"

Launching the connection

Once this is complete, it should be as easy as running

pon bluetoothconn

You should see in /var/log/messages

Jul 24 11:16:53 nine pppd[13645]: pppd 2.4.4 started by root, uid 0
Jul 24 11:16:57 nine chat[13662]: timeout set to 35 seconds
Jul 24 11:16:57 nine chat[13662]: abort on (nBUSYr)
Jul 24 11:16:57 nine chat[13662]: abort on (nERRORr)
Jul 24 11:16:57 nine chat[13662]: abort on (nNO ANSWERr)
Jul 24 11:16:57 nine chat[13662]: abort on (nNO CARRIERr)
Jul 24 11:16:57 nine chat[13662]: abort on (nNO DIALTONEr)
Jul 24 11:16:57 nine chat[13662]: abort on (nRINGINGrnrnRINGINGr)
Jul 24 11:16:57 nine chat[13662]: send (rAT^M)
Jul 24 11:16:57 nine chat[13662]: expect (OK)
Jul 24 11:16:57 nine chat[13662]: rAT^M^M
Jul 24 11:16:57 nine chat[13662]: OK
Jul 24 11:16:57 nine chat[13662]:  -- got it
Jul 24 11:16:57 nine chat[13662]: send (AT+CGDCONT=,,"3netaccess";^M)
Jul 24 11:16:58 nine chat[13662]: expect (OK)
Jul 24 11:16:58 nine chat[13662]: ^M
Jul 24 11:16:58 nine chat[13662]: AT+CGDCONT=,,"3netaccess";^M^M
Jul 24 11:16:58 nine chat[13662]: OK
Jul 24 11:16:58 nine chat[13662]:  -- got it
Jul 24 11:16:58 nine chat[13662]: send (ATD*99***1#^M)
Jul 24 11:16:58 nine chat[13662]: expect (})
Jul 24 11:16:58 nine chat[13662]: ^M
Jul 24 11:16:59 nine chat[13662]: ATD*99***1#^M^M
Jul 24 11:16:59 nine chat[13662]: CONNECT^M
Jul 24 11:16:59 nine chat[13662]: ~^?}
Jul 24 11:16:59 nine chat[13662]:  -- got it
Jul 24 11:16:59 nine chat[13662]: send (^M)
Jul 24 11:16:59 nine pppd[13645]: Serial connection established.
Jul 24 11:16:59 nine pppd[13645]: Using interface ppp0
Jul 24 11:16:59 nine pppd[13645]: Connect: ppp0 <--> /dev/rfcomm0
Jul 24 11:17:00 nine pppd[13645]: PAP authentication succeeded
Jul 24 11:17:00 nine pppd[13645]: local  IP address 117.102.131.229
Jul 24 11:17:00 nine pppd[13645]: remote IP address 10.6.6.6
Jul 24 11:17:00 nine pppd[13645]: primary   DNS address 202.124.81.2
Jul 24 11:17:00 nine pppd[13645]: secondary DNS address 202.124.81.3

Should be as easy as that, now just because of your telcos dodgey pricing schemes for mobile internet usage!