I can receive messages and the HDD unit reads back the messages from my iPHONE. But when I hit REPLY and pick a preformatted text like " I am driving. Will call later" and hit SEND, it gives me an error. I have not so far been able to reply to any incoming messages.
Prob your phone. I had the same issue with a BlackBerry, but it works perfectly since I switched to a Samsung Galaxy S3.