MrSeb writes "A recent study (PDF) conducted by UCLA professor Chunyi Peng shows that carriers generally count data usage correctly, but those customers who commonly use their device in areas with weak signal strength or to stream audio or video are often overcharged. Peng and three other researchers used data gleaned from an app installed on Android smartphones on two different carriers. The issue appears to be in how the system is set up to count data usage. Under the current scenario, data is charged as it is sent from the carrier's network to the end user. What does not exist is a system to confirm whether the packets are received, and thus preventing charges for unreceived data. Peng demonstrated this in two extreme circumstances. In one case, 450 megabytes of data was charged to an account where not a single bit of it had been received. On the flipside, Peng's group was able to construct an app which disguised data transfers as DNS requests, which are not counted by the carriers as data usage. Here they were able to transfer 200 megabytes of data without being charged. Overall, the average overcharge is about 5-7% for most users. While that does not seem like much, with unlimited plans gone and data caps in style that could pose potential problems for some heavy data users. Could you be going over your data allotment based on data you never received? It's quite possible."