That's strange. So you have a normal data plan from Telstra Internet for your HTC ChaCha right? Can your other apps access the net from your phone when you are not using wifi? Is it just Facebook that is not connecting or are you having other problems with your apps?
If none of the apps are responsive when you are out of wifi access it's probably a carrier issues. But if you can go online with your other apps then something strange is going on.
The Facebook android app takes its internet settings from the general settings for your phone and if one app can go online then they should all be able to. I just doubled checked in Facebook on my phone and there is no way to define other settings. I would check if your other apps can connect and if they can make sure your information is correctly saved in Facebook. If that doesn't work then I would call your cell company because if everything can go online but Facebook it might be an issue on their end. If nothing else works you could also try reinstalling the app.
Hope the helps.