AT+CHFA command is used to swap audio channels.
Simcom Module Tutorial
//Swap audio command support
+CHFA: (0 = NORMAL_AUDIO, 2 = HANDFREE_AUDIO)
//Current configuration is normal audio
//Set to handsfree audio
//Set to normal audio
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With Online AT Command Tester tool, you can test this feature.
With Online AT Command Tester tool, you can also get device diagnostic information easily,