Hi Dom
I have a similar problem so you are not alone. I used to have an Alfa Romeo Mito 2010 model and that was fine, I now have a Panda Cross and I have tried two different phones - they work fine for phone calls but if I use google maps the phone goes mute. The only way round this I have found (but defeats the point) is to switch off bluetooth on the phone, the phone then unmutes but that is not really the answer. I shall try and google the answer and if I have any joy I'm let you know.