When I use a bluetooth headset with my SPA525G, there are two huge problems.
First, the audio is scratchy, dropouts, etc.
Second, when the call starts, the person at the other end says I sound like I'm under water. After 10 seconds or so, it starts sounding better. BUT - then the volume in my ear gets louder and louder. I haven't touched the volume control. I finally have to move the earpiece off my ear.
So to sum up - at first too quiet, then noise starts creeping in, then the volume in my ear gets way too high.
I have loaded the latest firmware available as of 2021-02-10 - v7.6.2.f BT.
HELP! Otherwise this phone works great, but this is a deal breaker.