Hi friend.
Huawei ONTs later than V100R003C00 support this function. You need to modify the configuration file to enable this function.
To enable this function, perform the following steps:
1. Telnet 192.168.100.1 to log in to the ONT.
2. Perform the following configurations in the shell:
shellconfig InternetGatewayDevice.Services.VoiceService.1.VoiceProfile.1.Line.1.CallingFeatures. set MWIEnable 1
shellconfig InternetGatewayDevice.Services.VoiceService.1.VoiceProfile.1.Line.2.CallingFeatures. set MWIEnable 1
3. Return to the WAP and run the save data command.
Thanks.