Iphone 7 no data

My iPhone started losing data for no apparent reason. I updated the iOS and now it’s completely unusable. It says “cellular update failed. Your iPhone cannot make and receive calls or access cellular data until it has been updated. “

It took it to Cricket who supplied the phone and is the carrier. They said it’s an Apple problem and I need to call Apple care. I’m hoping there is an easy fix. Any help would be much appreciated. Thanks in advance!