Why can't I access the Internet while on a call on my Verizon Galaxy S6?

[Roamingnome3]

Yes you can talk and surf with 4g and/or wifi. But, the issue is with the advanced calling is that it is essentially voip and when your not in a 4g area or its not strong the voice service gets choppy and I've dropped many calls when my phone jumped from 4g to 3g. Plus if your in an area that has predominantly 3g coverage or weak 4g and no wifi you cannot surf and talk.

Advanced calling only works when you have 4g connectivity. So driving that back road on that road trip and you loose connectivity the whole deal is a bust. I do miss my old htc with 3/4g simultaneous data and voice.