internet data over VoIP over GSM - cheapest world wide roaming dataconnection

I have an idea for cheapest world wide roaming data connection (to
connect your Laptop to internet via gsm)

a) I have a SIM card registered in the UK on which I do not pay
incoming calls wherever I am

b) I have a VoIP provider which can call a UK sim for 2 cents a minute
(it can connect my mobile with a fix line for the same price)

Therefore I can call world wide in roaming (being in almost any
country) for 2 cents a minute from my mobile instead of 1 Euro of
standard roaming price.

Now I would like to connect to the internet by dial-up.
a) I got a fix line number to dial up. eg +4820XXXXXX
b) I got my mobile connected by bluetooth to my laptop (as a gsm modem)
c) I set my Windows XP for internet callback service - so it answers
the call when it is being called
d) now by sending a text Ito my voip provider to connect two numbers -
to trigger a connection between my mobile and the internet dialup
number +4820xxxx (the service like www.jajah.com or like
www.voipcheap.com)

I am hoping that:
1) windows will answer the call on the mobile
2) the call will be connected to the dialup provider on +4820xxxx ( all
this happens via IP but my GSM and my laptop thinks it is a normal
call)
3) I am able to surf on the internet wherever I am in the world for 2
cents a minute!!!


So this is the theory. In practice my mobile connected via bluetooth
indeed receives the call but after a second it hangs up.
Does anybody has any experience on connecting to the internet via
mobile but on the call back?
The fact that it goes over ip is transparent for me it makes only the
connection very cheap.


cheers
Paul