i think most people had the option to choose among two, or maybe if they were lucky three ISPs. only big cities had more, and the better alternative ISPs tended to be more expensive too. and since they were not exactly telling you in advance that they were going to do this and they often were locking you into one or two year minimum contracts, switching ISPs was and still is not a simple thing to do.

I haven't subscribe such ISP in person, but there are many cases from Internet, it reminds me that never trust any ISP (or Gateway that could inspect data):

https://security.stackexchange.com/questions/70970/my-isp-is...

https://security.stackexchange.com/questions/157828/my-isp-b...

https://github.com/net4people/bbs/issues/19