13 days ago I received my BV8000Pro, I have problems with the audio of my phone calls, they do not listen to me or they listen badly or the volume is turned down in a moment, this happens to me in different calls, in a moment they hear me well and then something happens, now I'm changing my SIM as a last alternative, what can I do? for the rest everything is very good, but my phone will not let me speak on the phone ..., I hope your answer, regards Hectorcc

Be sure there is no finger in front or dirt inside the microphone hole. If that don't help try to update to the latest firmware and perform a factory reset after that.