Changing MAC address & Ip address on a mobile broadband card?

[MOONCRICKET]

Does anyone here know if it is possible to change your ip on a mobile broadband card? Theoretically, you would need to be able to change the mac address of the card.

I am mostly interested in Verizon and Cricket's offerings. It would be nice to check ebay from my laptop wherever I happen to be.

[aspkin]

I'm pretty sure every time you connect to these cards, you get a new IP.