What app can i use to read someones messages off their phone without them knowing

[level]

What app can i use to read someones messages off their phone without them knowing. for an iphone?

I google search and find "HelloSPY" app. It's FREE GPS tracking forever and have many features. Such as: Read SMS, Call History, Track iMessages and WhatsApp message, Spy Call and more.

Do you know it? Thanks many help!!!

 

[idontknow]

Why would somebody want to read somebody's messages is hard for me to understand....i hope there are no apps for that!