Phone calls causing echo

Recently, every time I do a phone call, the person I am talking to has an echo. I don’t hear it, but they do. The speaker is off. When I connect a headset, the echo is gone. I consider this a workaround, because I don’t always have a headset with me.

I can’t really tell since when this issue stated to occur. Maybe one of the latest /e/OS upgrades?

How can I fix that?

What’s your phone model?
Maybe this one?

I should mention, that my setup is pretty much the same: Samsung Galaxy S7 with /e/OS 1.5 (Android 10).

I have two other friends who have the same setup (Samsung Galaxy S7 with /e/OS 1.5) and also experience echo on the phone of the caller.
It happen all the time if there is no headphones.
It doesn’t happen if there is a headphones connected, or if the call is made over internet (what’s app, signal, messenger, …)
This is quite annoying and I don’t see any solution until now, does someone have any idea what could we do ?