Hi mano,
I have not had this issue from Q5 bluetooth,in fact its a million times better than the old one we had on the a4,only thing i can think of is that the micro phone sensitivity is turned up to high.not sure if this can be altered via mmi or not or wether it needs a dealer to sort it(unless you know anyone with a vag-com/vcds set up that can do it for you.
Rich