TLX15

I picked up an iPhone 7 and a 2016 TLX AWD Tech within a few days of each other. I connected to the Hands Free Link easily, and Bluetooth music played fine, with slightly less lag between my inputs and the system's response than I saw in my 2015 TLX. The thing is, once in a while, when using the steering wheel controls to make a call from my speed dial list, the audio in the car and on the other end sounds as if we are under water.
It is muffled, as if I have my hand over my mouth, and very low pitched, like Darth Vader. When I called Apple, the rep told me that since this happened only in the car, it is most likely the car. Reading some previous posts in this forum, I found one fellow member had luck disconnecting the negative battery terminal. This did not help me.

So I wonder...
Has anyone else had this problem?
Are there any other suggestions?