This reminds me of when we were the first ISP in France (we had a thing that was basically Compuserve with Internet bolted on — now some people will know what that was :-/).
We were at some kind of expo, I was the tech guy, I was with the cute sales girl. For historical reasons, we started with mostly Apple clients, then opened to everything else (this was the early 90s in Europe).
Anyway I was playing on my Linux machine (yay, early adopter) and she had a hairy guy that came in that was enthralled with the whole thing. So she spent a full forty minutes with him, explaining the whole local forum things, the Internet, the Usenet, the email, the whole shebang, the guy loves it.
So he really wants to sign on, but when he's filling in the papers, he's stuck.
"Is it ok if I leave that blank?"
"That" was the phone number. The guy didn't have a phone line. At the time all accesses were through a modem. No phone line, no online access. The wonders of the online world were forever beyond his reach.
It took another ten minutes to get this through to him.
As a high school student, I had a job like this for about a week. On my last day, I received this call just like yours and I said “You are quite possibly the stupidest person I’ve ever interacted with” because they were yelling this type of nonsense and screaming over me.
I do not regret my exit to the call center work life. You people have a special type of patience and deserve to be paid far more.
I mean, nowadays you can get wireless internet – via LTE/5G. For technologically illiterate users, I’d put the blame on whoever sold them a WiFi router.