This sets up perverse incentives, that as far as I can tell, are theoretical, but have potential to become more prevalent. Because of the cost center as a profit center idea, my ISP can generate more revenue by providing less value to me. If failing infrastructure causes me to call support more often, and more support calls increase the likelihood of more revenue, why should the ISP invest in better infrastructure?
The key to having a successful business is to carefully align the incentives of specialities in an organization to make the most competitive offerings to the market. If there are competitors, and customers can switch to them, and the competition is more compelling, then I would go to other ISPs.