>>Think about if more people did this. Suddenly those lobbyists voices would get a lot less powerful.
No they wouldn't. Lobbyists represent moneyed interests. You don't. You're just one person.
Seriously, you are committing two mistakes here. The first mistake is to assume that your letters and phone calls to representatives actually matter. The second mistake is to assume that your representatives have any power to stop our rogue intelligence agencies, particularly the NSA.
I want to address the second one first, because it's more important. Simply put, the NSA is out of control. They have an extremely sophisticated apparatus in place that has been growing exponentially in complexity and reach since immediately after 9/11, and they have the balls to lie to the Congress about it while under oath. And there are secret courts - secret courts! - that seem to give them blanket approval with absolutely zero accountability. An organization like that cannot be stopped, not just because it's political suicide to try to stop them but also because it would genuinely cause a lot of collateral damage.
But the other point is also worth addressing. The idea that writing or calling your representatives actually affects anything is an illusion. An illusion that must be maintained to keep things stable, but an illusion nonetheless. Because here's what actually happens when they get a letter from you: they skim through it and send you a canned response. That's it. Your opinion does not matter unless you have deep pockets and are an existing or potential donor. This is difficult to accept for some people but it is the reality.