Shade, Dub is right, your recourse is the seller, in this case your carrier.
I think Dub is also suggesting you can try troubleshooting this yourself before you go back to the carrier again. And that's not a bad idea.
Where do you stand now? Is it the same place you describe in the first paragraph of your original post? Your account is in good standing, there is no problem with your account setup on the carrier's end, the device shows good signal, but still you cannot make a call or send/receive SMS/MMS? Is that it?