As I already mentioned, my sales job in the 90s wanted me to have a mobile, but would not provide one. So, I bought one, and I'd get sent a bill every month, which I'd then send to the company. The bill was $500+ a month, as I was the sole employee in my state, I spent a lot of time on the road, and on the phone. I got a call one day from Optus. They gave me a new Erikson digital phone if I'd swap to them. Now, this is the days before plans and so on, this was so amazing to me that I pulled over to clarify. Then, I said yes. I called Telstra and told them I wanted to disconnect my service, and they accepted my disconnection request.
I worked in Tasmania, and I had to get the bills, send them to Melbourne, and then my boss would, once a month, send them to Sydney to get paid. On that basis, I frequently got second notices, etc. I got a disconnection notice about 6 weeks later. I called and said something along the lines of "As I've explained before, I have no control over the payment process and it can be slow, but you will get paid. I still found it funny that you'd threaten to disconnect a line that is not connected". They informed me the line WAS connected. I was on a plan where I prepaid $500 a month in order to get a better call rate, a casual plan would have cost $1000 a month or more. I asked why they thought I was paying $500 for connection when I was not using my phone, and they indicated they did not care.
For the next few months, I was getting angry bills and threats in my PO Box. I talked to my boss about it. They would have paid, but I refused to pass it through on principle. I disconnected the line, it was clear from looking at the situation that I believed it to be disconnected, and I was not paying. After quite a few months, they stopped contacting me. This was when I decided to never use a Telstra service again. Sadly, over time, I found I had no choice but to reconnect to Telstra, but that's another story.