Before you go to the trouble of being put on hold by your ISP you ought to take a moment to figure out which of the steps you took solved your problem.
Actually, my new ISP is pretty good about customer service and has a fairly large group of people dealing with issues. The last person I dealt with gave me an email I could use for future problems and the website has on-line chats, answered fairly quickly. My old ISP is in the midst of letting about 6,000 people go.
I also may have spoke a bit too soon about "problem solved" as the emails I received, and which went to my Inbox, were from an iPhone. This morning the Sender did two additional tests from the laptop (a Windows machine) in the office. Both had Windat attachments and both went to junk.
One wrinkle in all this is that the emails say "You marked this as Junk" which I would never have deliberately done. However, when I looked at my Tool Bar, the default layout has the "Mark As Junk" right next to "Trash". It's quite possible an email was assigned junk status in error. I have now rearranged the Tool Bar.
