There will be no guarantee. But there will be multiple service providers for people to choose from. Competition between service providers will push consumers to the better service.
For example, suppose Verizon obeyed net neutrality whereas AT&T did not, favoring instead their own content. Consumers would naturally choose Verizon because their connections were not being throttled. If enough consumers move, it will force AT&T to respect net neutrality as well.
For example, suppose Verizon obeyed net neutrality whereas AT&T did not, favoring instead their own content. Consumers would naturally choose Verizon because their connections were not being throttled. If enough consumers move, it will force AT&T to respect net neutrality as well.