Different continent (Europe) but something similar happens with my provider (Orange).
3G works perfectly to make phone calls (since VoLTE is a bit of a disaster here, most phones don't work with it) but for data is pretty much hit or miss. Some antennas seem to provide Internet and in others even ping (to 8.8.8.8 or 4.2.2.2) doesn't work.
I’m in Ontario, Canada and whenever my phone loses LTE and shows full bars 3G, the internet doesn’t work at all.