I use the built-in speakers too. When I turn the volume to 0, I do not hear anything.
Man, VIZIO tech support is horrible. I can never get through. I have to go to Sales to get to tech support. But, as usual, the manager was not available. I left my number. Let's see if he calls me back.
I will never purchase a VIZIO product from any other retailer expect Costco. Not worth the downside!
If you purchased from Costco then return it. If you purchased from somewhere else and the return period has ended and you must deal with VIZIO, you have my sympathy.