The Signal messenger and protocol.

Yeah, I cannot make Signal display voice call to full screen on Samsung Galaxy S20. It is only displayed as a notification bar. Also on the lock screen it is not displayed at all, it just rings, and there is no even notification bar. When you unlock (actually it has no lock, just swipe) a phone still nothing, you have to open the top notification panel to accept or deny a call. I really need it for elder, that is not able to see a notification bar. I need it to be displayed in full screen, just like a normal call.

Could anyone help on this problem? I'd be grateful.