We enabled AT logs and the situation is the following:
We can send SMS with the HTTP to SMS link (sendsms?username,password,etc.etc), but cannot send sms with the builtin SMS Sender utility in the GUI. Strange.
If we are looking at the AT logs, then we can see that the commands to send SMS is happening if we are using the link, and not happening if we are using the GUI.
The receiving is working as expected with the latest firmware.
I will add you on skype and then you can see our device if we can organise it.