Fail to install managed profile

I need help to get past an error message on an iPhone 6, please.

The error message says:

"Configuring iPhone

Installing configuration from [employer]

Profile Installation Failed

Porfile Failed to Install"

Special details about this phone:

By design, it can't make phone calls. The phone number associated with the iPhone 6 was ported to an upgraded device.

It was my work phone, and I was using it for personal apps and storage.

My employer tried to remove the managed profile from the iPhone 6, but I still see this error message.

When did the error message start:

I didn't realize the managed profile was still on the phone.

I upgraded the iOS to 15.5.

Now I can't get to the Settings or any apps.

I'm hoping there's a way I can remove the managed profile or rollback the iOS update so that I don't risk losing data on the device.

At the Genius Bar, the tech advised having my employer remove the managed profile. My IT department says they did it, but I still have the original error message.

Thanks for any ideas or support!