Hello!
After logging in to the web page of the device, choose Voice > SIP/H.248 Protocol Conversion
to switch the VoIP protocol to SIP or H.248.

Note:
1. The navigation tree varies according to the device model.
2. ONT V300R012C00 and later versions.
3. Exercise caution when performing this operation because it will interrupt the ongoing call and delete current data.
Thank you!