heya
not sure what you want to do here...
do you have broadband voice (bt voip)?
if yes, you can call between telephone systems for free anyway. no need to create a tunnel.
if no, then you should go into your 2700 (type 'home' into ie address bar) and change the firewall>firewall settings. open the ports for your software. i reckon there will be an faq up for this in the broadband section.
hope this is helpful.
