As for the possibility of spending money, just to run a diagnostic on the phone would cost $35. That should be free -- as far as I know, the problem isn't even with the phone. But apparently, mobile providers offer phone service for low prices and try to earn all their money on additional "services" like this one. Or, I could but a new phone from them for at least $150. Or, I could wait until August and get $75 off the price of a phone from them. Or, I could buy a phone on eBay.
But, as I said, my first goal was to get my wife a working phone. They'll switch numbers between phones for free. I was going to switch her number to my phone and then deal with the non-working phone in "Phase 2" of the solution. However, to transfer numbers between phones, a third "dummy" phone is needed. Enter old phone that we were lucky we kept. We got rid of that maybe 2 1/2 years ago because the screen no longer worked. I plugged it in and the screen worked. So, instead of having the non-working phone, I transferred my number to the ancient Samsung 8500. We'll see how long that works. I'm thinking eBay is the next option, if this one doesn't work out.