How can a call be tapped on a cellphone?

I believe not, i have had many friends try that, and ultimately fail. Infact if i recall correctly, they were the ones that ended up getting hurt from it all. This is because the app they used to attempt that action was a per month payment from down inside the small print. and as for tapping into calls manually... maybe, but i'm not sure. My first thought would be that tapping into people's calls was illegal. And it very well maybe. I'm not totally sure to be honest. :)