[BenjaminRo]

Does anybody know how to fix this? Like with an app or a Android O/S update?

[B. Diddy]

Welcome to Android Central! I moved this from the Note 4 forum to the J Series forum.

Which carrier are you on? In order to have simultaneous voice and data, VoLTE has to be supported (and although this is supported by Verizon, AT&T, and T-Mobile, I believe Sprint still hasn't completely rolled it out in the US).

[BenjaminRo]

Thanks. You're welcome. I'm a O² subscriber. Is it a cellphone problem with the multiplexing J3 (2016) or is the problem on the side of the telephone company?

[B. Diddy]

Did you get your phone from O2, or did you bring it to O2 from somewhere else?

Look in the Settings>Mobile Networks menu and look for an option for VoLTE. It might be called various things, like Enhanced 4G, Advanced Calling, HD Voice, or others.

[BenjaminRo]

I bought it from Amazon and subscribed to O² later. All I have in it is 2G, 2G&3G, LTE/3G. Can I activate the extra feature somehow?

[B. Diddy]

That's not the menu option I'm thinking of -- it sounds like you're looking at the Preferred Network Type option. If you can't find the option I suggested, then the phone's firmware probably doesn't support VoLTE.

[BenjaminRo]

Ok.