How do I stop my phone auto connecting to random wifi networks?

[Andyvalver]

I'm pretty sure this had been happening since lollipop. I leave wifi on and when I go out it connects to random networks even though I have never used them. This means they don't actually work for me. It's a pain because I can me messaging someone on what's app only to find it won't send because my phone has connected to a random network that makes it override 4g. Can't find how to stop it. Getting on my nerves. Before it used to show a network was available but not connect to it. Any ideas?

Andy.

Posted via Sony xperia z2