How to Opt Out of AT&T's Plan to Sell Data About You and Your Smartphone Use
forbes.com
forbes.com
All you need is a smartphone,wifi, and your favorite secure chat/voip software like chatsecure, redphone, textsecure, etc.
I will admit this sometimes leaves me without internet for up to 10 minutes, but I have cultivated a stoic mindset that lets me survive those periods.
Most Europeans have public wifi. Att does not operate in Europe :)