Is the call quality good?

When you make a call from the Onoff application, it is redirected through your SIM card, so there is no loss of quality.

When you receive a call, by default, the application offers you to take this call using the Internet network: a VoIP ("Voice over IP") call. However, depending on the state and quality of your 3G/4G network or your Wi-Fi connection, it is possible to observe differences in call reception quality.