Maybe...except people in congress have private lines which they use to communicate to the people they need/want to talk to. The public lines are only used for constituent and other public calls. So really what you'd be doing is blocking their constituents from calling them.

So the congressperson isn't losing any calls they needed to take and the only person being punished is their secretary. In the worse case scenario that congressperson could have a bunch of constituents who object to SOPA and you'd be blocking those calls with your own (which the congressman couldn't care less about if you aren't in their district)