I'm not sure if you have heard that Verizon (VZW) has been, for the past two years, inserting a perma-cookie into HTTP traffic headers via means of a UIDH. The UIDH ignores: private browsing, do not track, even Verizon's own opt-outs.
I have assembled some links below to provide you some more information regarding this issue.
AFAIK, AirVPN users are safe from VZW tracking. You are also safe on sites that use HTTPS.
According to some comments in the various articles (links to articles below), it appears at least AT&T is doing the same thing as VZW.
LessonsLearned: Test for Cellular tracking Beacons (must be on cellular network)
This issue highlights the need for net neutrality and encryption!