how to Auto receive a User Mobile

this is my first day in this section. I don't know anything about mobile programming. I want to do something, suppose i call in a mobile number and it will autometicly received. But the mobile user will not informed. and I can hear all things happening there.

Is it possable then please inform me what have to do for this?
Bye from
Rummy

So you want to spy on people without their knowledge?

Don't think so

Is there any possible benign use for that?