My sidekick lx 09 isn't connecting to the internet?

[Bobby]

I just bought an unlocked sidekick lx 09 off of Ebay so I can use it on my At&t plan. It works fine and I can send and receive messages and same with phone calls, but when I try to use the internet it doesn't let me and it also says that the service is unavailable I have the right phone plan with the data things so I'm just wondering if there's something I can do to make the internet work? Thanks