We had a computer with dialup but it was insanely expensive to use there at the time and only my parents could use it.
Well one day they left me home alone and I got curious so I connected and stayed online for probably 8-9 hours before they got home. It was a blast. I too was also hooked immediately.
I sure got a shock when my parents came into my room a month later to ask if I had been on the computer without them because we had a huge bill haha.
Luckily I had a spare keyboard and mouse in my cupboard, which I promptly set up to the bemusement of my parents. They were very patient...
I bought this little box on ebay that monitored for the call waiting signal while dialup was connected and then let the call ring through. If I was quick I could get starcraft to reconnect when a telemarketer interrupted. It was a lot cheaper than a second phone line!
Eventually I managed to shoulder surf the login for the PPP connection to a local ISP used at my school, then I had unlimited. Thankfully I had enough sense at 13 or 14 to ATDT*67,,1xxxxxxxxxx so that they couldn't identify who it was without actually sending a subpoena/warrant to the telco (which they didn't do). In any case the school paid a flat rate for unlimited usage, so my being connected all night didn't cost anyone anything.
They yelled at me a lot though because it was pretty obvious who was using dozens of hours of dialin every month, given that the school's list of suspects was one item long.
Unlike you, I didn't have enough foresight to attempt to block the dialing in number .. at all. But I had internet for most of the school year until, as per your story, it relatively came crashing down one day.
Same justifications of "borrowing" the account as well -- I wasn't using it during the school day itself, I was at school -- and it seemed so silly to waste such services for 2/3rd's of a day!
A Stern talking to and that was that... Imaging what would happen now!
Not sure why they didn't change the password. I was assuming they just never noticed the usage.