I can say that m a proud owner of this fone J7. I haven’t faced any prob with calling n hearing while engaged in calls.
Voices r clear n loud from both sides( caller n receiver).
I haven’t tried group calling but that depends on the network we r using, other wise the fone is great in every xpect. The exterior is not that much promising but they made it a HUGE sturdy and in inside it is packed with bunch of goodies,