Topway TS7 Android Car Stereo MIC Volume - Low Volume issue. Very tricky, you will not notice mic volume bar as it stays only on screen for 2 seconds and comes up everytime only when bluetooth is disconnected and connected and the first call is made.
By default the mic volume is very low. This video is shot with volume already kept at max. Note this car stereo unit does NOT have explicit mic volume menu in settings. Hope this helps.