I’ve seen quite a few posts circulating that cite the UNDHR as a tool that can be used to fight the repeal of net neutrality and although it exists, it can’t be used to actually do anything.
The United States may have signed the UNDHR, but they did not ratify it, meaning that it isn’t legally binding. As it is not legally binding, citizens can not seek recourse by invoking the clause that declares the internet as a human right.
The United Nations is in no way some international government, it cannot impede state sovereignty. Therefore, it cannot interfere in this battle. Other countries can try and deter the US from repealing net neutrality through their foreign policy, but frankly, it would actually hurt their economies more given the hegemony that the United States exercises over the international system.
However, when contacting your representatives, you can invoke something like the US Constitution. Article 1 of the Constitution is about protecting free speech in public spaces and the internet counts as a public space. Telling your representatives that repealing net neutrality would violate your constitutional rights might make them more inclined not to vote for it.