A lot of the debate and discussion about Network Neutrality is about tiered service, that ISPs will charge different amounts of money to both ends of a connection based on traffic priorities set by their own best interests. Meaning that if Comcast offers a VoIP service, they think they should be allowed to restrict access to competitors’ VoIP services (through outright denying connections or by traffic shaping to limit bandwidth) to encourage their customers to use their own services. In some respects, this could be considered double-dipping. From a business standpoint, if it makes sense for a company that already has unreliable service and problematic customer service (but I use Comcast solely as an example here, they are hardly the only provider to think like this and to have problems) to spread themselves thinner by expanding into other products is left as an exercise for the reader.
But this is only half the debate. ISPs can charge whatever the want if consumers of their services have an option to go someplace else: doing so is the bedrock of competition in the marketplace. Many ISPs are a monopoly in their area and have no effective competitors. Being allowed to be a monopoly and having common carrier status go hand in hand. If an ISP is going to restrict or limit the kinds of traffic that goes over the connection that the customer is paying for, they should lose the right to be a legally recognized/mandated monopoly. If there is proper competition for the base packet transfer service (”Internet service”) and the ISP is not a monopoly in the market (rarely the case in most major metropolitan areas in the US) then they should be able to set prices and restrict services however they see fit and let the market decide if doing so is a good idea for the company.