I don't know what steps you've tried; perhaps you already tried these, but just in case, here they are, the most drastic being #3; if you go that far, make sure you back up all your contacts and data (via Samsung Smart Switch, a cloud, etc...).
#1 Go to Settings/General Management/Reset/Reset all Settings: choose that option & confirm choice.... (see if this fixes anything for you.)
#2 Go to Settings/General Management/Reset/Reset Networkl Settings: choose that option & confirm choice.... (see if that does anything)
#3 Go to Settings/General Management/Reset/Factory Data Reset: choose that option & confirm choice.... (Once again, make sure you back-uip everything before doing this step)
Let us know if any of these tips help, OR if you already tried them and they didn't.
You wouldn't expect Samsung to sell "non-working phones"!!! - - And on top of that, their "custromer support" is TERRIBLE! And of course, you need your phone for business... if you don't have a back-up phone, maybe you can get an inexpensive phone just to get you by. - - Good luck!
Be sure to click " ✓ Accept as Solution" when you find an answer that works for you. - Thanks!
Resetting the Network settings did the trick for me. Wish I did that first. Resetting All Settings created a pain in the rear getting those settings back to normal.