Become a spy using a mobile phone

Its simple to become a spy using a mobile phone.Tools required for this work are singe mobile phone with some call balance and a land phone (bsnl connection in India) in the place where spywork have to be done. Also we should know that land phone number(if u dont know, you can use directory to know the number). Then call in that number using your mobile phone then talk something and then apolagise for dialling the wrong number. Then wait to disconnect the land phone for a while by them. Same time u should not press 'end' button of your mobile. Now you can hear everything in other end without any risk and going there. Yes , now you also become a spy with out moving a step from where you are.Same method can be used to black incoming call to a number.