Normal local hang up error

Question

Sometimes, not always, but most of the time, when calling outside the call ends with the "normal local hung up" message.

The receiver hears a ring.

This is not my provider's fault, cause I use the same service with zoiper on the Mac and I never face such an issue, so it has to be related with the Android app.

I have a Samsung Note 10 plus.

Any hint?

Thank you.