Linux : Ubuntu 7.10
Provider : XL & Centrin
Mobile : Nokia E61
using Bluetooth (Dial Up Network/DUN) service

Create new file /etc/ppp/peers/centrin

connect "/usr/sbin/chat -v -f /etc/chatscripts/centrin"
usepeerdns
noauth
defaultroute
noipdefault
nocrtscts
nocdtrcts
modem /dev/rfcomm0 115200
user "user@xl.centrin.net.id"

Replace user@xl..... with your username given by centrin.
File /etc/ppp/pap-secrets, add this line at the end of the file.

"user@xl.centrin.net.id" * "mypassword"

Also replace the mypassword with your password.
Create new file /etc/chatscripts/centrin

TIMEOUT 60
ABORT ERROR
ABORT BUSY
ABORT VOICE
ABORT "NO CARRIER"
ABORT "NO DIALTONE"
ABORT "NO DIAL TONE"
ABORT "NO ANSWER"
"" "ATZ"
OK AT+cgdcont=1,"IP","centrin.net.id"
OK-AT-OK "ATDT*99#"
TIMEOUT 75
CONNECT

Prepare your bluetooth connection, so your computer can see your mobile phone. But somehow I cannot pairing from "Bluetooth Manager" :-( .
CLI rulezz .... :-)
Next, some commands need root priviledge.
Search for device and channel for Dial-Up Network.

$ sdptool search DUN

In my case, the device-id is 00:12:D2:6B:1F:4F
and the channel is 2.

We'll use rfcomm0 . So release old connection, if any.

$ rfcomm release 0

Bind the device, use sdptool's result.

$ rfcomm bind 0 00:12:D2:6B:1F:4F 2 

Next, we need to pair your computer and your mobile-phone.
Well, I don't know how to do it better. Please advice ....
But we need to open xhost security.

$ xhost +

Place the PIN at the handset.
Match the Bluetooth PIN at the Ubuntu.

$ cat < /dev/rfcomm0

Control-C to back to prompt.
Then close the X security.

$ xhost -

Then call the pppd

$ pppd call centrin

Happy surfing ....