Oh No! I can't imagine how frustrating it would be to not be able to send text messages. Lets look into this immediately. I'm sure working together we can get this resolved.
Please remove the battery from the blackberry leave it out for 30 seconds, then reinsert and retest. What is the model number for your Blackberry Curve?
Have you changed any settings? Is Wifi turned off? If not please do so and retest.
Please also ensure your Firewall on the Blackberry is disabled. Here's a link that will show you how to disable your firewall. Please choose your device and it will give you step by step instructions.
Let me know if this helps, if not I will further troubleshoot with you.