Except in this case (cellular service), there is at least some competition. And FaceTime isn't particularly a good example, as AT&T reversed their policy without Net Neutrality rules in place. Competition, at least in this one example, worked.
After official complaints lodged with the FCC. Also, this was during the time period of the 2010 open internet order[0] and the 2014 court case[1], where ISPs and the FCC thought that the FCC had the authority to enforce "no blocking" violations.
So, saying "without Net Neutrality rules in place" is incorrect.
[0] - https://en.wikipedia.org/wiki/FCC_Open_Internet_Order_2010
[1] - https://en.wikipedia.org/wiki/Verizon_Communications_Inc._v....
The carriers deployed proxy infrastructure to inspect and control traffic and were definately experimenting with limiting apps deemed disruptive in the 2013-2014 timeframe. If you had an app that generated lots of small packets in a short period of time, you’d run into it on some networks.