You won't be able to fix it, at least not until our friends at Apple update the iOS again. I have the iPhone 5 and it's the same. You can receive/listen to text messages, but you cannot reply/send by voice.
There is some element of the Bluetooth messaging protocol that is missing from the Apple iOS. Surely this will be addressed in the next iOS, as they are behind Android in this regard.
This link seems to support this: http://chrysler.servigistics.com/que...=en&brand=Jeep
If you run through the menu there, you will see that we do not currently have the ability to send. Sucks.