One solution that fixed this issue with my ISP was that when I went through the first and second line and got in touch with the people that fixed my problem, I asked them if they could give me one of their personal numbers in case the same problem happened again. The problem did occur a couple more times, and I just directly called the same guy.

Tech support works with scripts. Just get to know these scripts by heart and answer all questions from the script you can in one long sentence, before they ask it. Like in "Hi I have a problem with this and that...I have restarted the router, I have checked the cables, the red light is on, the green light is off, not other lights are blinking......etc.etc.etc. That way the person at the other end of the line can just go click-click-click and you'll be 10 steps further in their script in 5 seconds.

More importantly, using a plain email would save lots of time and effort. As a goal-driven-lazy person, that’s a good enough reason to start experimenting.