How to turn off automatic downloads?

I have a new 14" Mackbook Pro and I have unchecked everything except "Check for updates" in Software updates and still it is downloading some kind of updates in the background. I need to turn this completelly off. Please tell me how someone.

I am on shared internet from my mobile as there is no WiFi in my location. I woke up this morning and tried to have a FaceTime call from my phone but the connection was really poor. I noticed then that there was a connection to my shared internet and I thought that was weird as I had not even opened my MacBook yet. I opened it and had to turn of WiFi as it was using all my data doing some kind of download in the background. While sleeping. I need to turn this off! I want to download updates only when I am connected to propper internet, not my phone.