Net neutrality has its historical roots in how telephone lines work. While using a telephone line, you can dial your preferred number and connect to it right away. It does not matter whether you are connecting the call from Operator A to Operator B, nor does it matter if you are dialing the number of a vegetable dealer or a drug dealer.
The operators neither block access a specific number, nor do they delay connections from the number, unless requested by the law. In most cases, the countries have certain set of rules that allow the telephone operators to provide unfaltering and unfiltered services to their users.