The amendment doesn't say "secure from government" or "secure from law enforcement." It just says "secure."
A person cannot sell themselves into slavery. Yet we allow the US government to endorse indentured servitude for immigrant labor, because corporations want indentured servitude.
Nor can a US citizen sign away workplace safety rights, legally. Yet we allow US construction companies to rampantly hire off-the-books undocumented labor so that they can freely ignore workplace safety rights, since no one will exist to make claims against them.
It would have been perfectly reasonable for a court to broadly ban surveillance of individuals by telecom companies back in the 1990s, based on the same principles that those courts have willfully violated on behalf of corporations in the other examples above.