Sending sms from tablet not allowed or not possible?
The hardware and software support SMS, but not calling. The most likely explanation is that your contract is a data-only contract and SMS messaging is disabled by your operator. 

There is a chance, however, that the problem is your SMS settings. You can check these by opening Messaging, then open Settings from the top right corner and check that the Message center under Text message (SMS) settings is correct. The Message center number is network specific, so check it from another phone that uses the same network or ask your operator.