I can't send or receive any text messages

First, check whether your handset is configured correctly. 

Having problems? Then try this:

• Restart your phone. Do you still have a removable battery? Then try removing it and putting it back in.
• Still having problems? Place your SIM card in another handset and check whether it works there. Then place your BASE SIM card back in the original handset, test it again and check whether your text message has been sent/received.