I'm having this same issue with my Note 8 going from 4G to 1x when I make a call, I then cannot use the internet and talk at the same time. I disabled HD voice because I kept getting complaints from the people on the phone with me that they hear EVERYTHING around me and my voice is really drowned out. I'm in a pickle here, everyone I talk to that doesn't have Verizon doesn't have this problem, everyone.