T-Mobile and 360 on xbox live

Hi all, I'm using T-Mobile Web n Walk with 10gig download limit and the E170 usb modem. i've been using ICS through my laptop to play the 360 over xbox live, and i have to say T-Mobiles service is great. I live in a good coverage area and my download speeds never drop below 400kbs, reaching 1200kbs at best but averaging around 600 to 800 kbs, this is plenty enough for gaming and i'm amazed at how well it does work to be honest. the only problem i have with it is that my NAT settings are on strict which means i can't hear or talk to some players and have trouble joining some games. I've been told that this is due to T-mobile giving me a private ip address which in affect means their controlling my NAT. Can T-mobile change this for by say giving me a public ip or opening my NAT up, or whether this may change in the future with mobile broadband becoming more poplar? would be a shame if they can't as it i's a great alternative to having BT for line rental and £123 for a line to be fitted.