Automatic switching network problem

[mauimarco]

Not sure when it started but everytime I live. You house the phone should switch to my data plan instead it propose a window asking me if I want to switch networks. Most of the time the phone is my bag so I forget to check n this wouldn't be a big problem except that the phone get very hot n discharge battery very quick. I think it is trying hard to connect to Wi-Fi instead of automatically connect to my phone internet data plan. Wondering how to fix this annoyance. Thanks, marco