A flip phone doesn't really stop surveillance. They still track where you are, who you call. Sure, maybe no app data, but since you don't use Facebook and such that data wouldn't be there anyway.
http://www.washingtonpost.com/world/national-security/nsa-gr...
By September 2004, a new NSA technique enabled the agency to find cellphones even
when they were turned off. JSOC troops called this “The Find,”