Why Won't My Basic Phone Receive Calls?

[LEGRANDEMA]

All basic phones on my plan are missing calls.  Phone won't ring, and won't register a missed call.  Phones have been updated.  One has been updated twice in 2 weeks.  Same problem.  Why is there a sudden problem with supporting basic phones???? At a loss.  Can't give 89 year old father a smart phone.  Am being told the only way to resolve problem of missed calls is to go to smart phone.  What's going on?????