GPRS w/Bluetooth - NO DIALTONE?

[Jesu]

I'm trying to use bluetooth to make a GPRS dialup connection from my ibook to my nokia 7650, using a USB bluetooth dongle. I'm pretty much there, I can l2ping the phone, I can send files back and forth over bluetooth, and I can get as far as setting up the modem emulation on /dev/rfcomm0, but when I try and interact with it through minicom I get:

AT
OK
ATE1
OK

But then either:

AT+CGDCONT=1,"IP","orange.co.uk","",0,0
ERROR

and it refuses to talk to me anymore, or:

ATDT01132xxxxxx (my home phone no.)
NO DIALTONE
ATDTATD*99***1# (GPRS no.)
NO DIALTONE

I'm pretty stumped as to where to go from here - I'm pretty sure there's enough signal where I'm trying it, and because of
http://www.teaparty.net/technotes/blue-gprs.html ("Using the GPRS") I would expect either a message on the phone or a different error condition if it was out of range. Certainly there's enough GSM signal, and that doesn't work either (though it works as a regular phone...)

Anyone got any ideas?

Thanks,

Jesu