Security cameras

I have security cameras, I can access them from an app on my phone only when I'm using the home Wi-Fi. If I turn the Wi-Fi off on my phone or am connected to someone else's Wi-Fi, I can not access them. Also, I can access them on my desktop by entering the address into a web browser but I cannot download any of the videos. 

Any help is appreciated. 

Hi Paul,

Would you happen to know what brand of security cameras we are talking here?  Perhaps they have a manual you can access online for further help?