How does iPhone SE hardware test work?

It's been very difficult to access the SE hardware test, given that my ISP's password was not easy to find and the trick of holding down two buttons while plugging the phone in is a knack to be learned. Anyway, that was all done and after the best part of an hour, all I learned was I should contact Apple Support at a URL. Is that it? It was a waste of time. The reason I wanted to test my phone is that a family member keeps finding that she can't hear me intermittently. She says it is not a problem with any of her other contacts and is blaming my phone.