An anonymous reader writes "Joel Runyon recounts a tale that will be familiar to many people who have bought secondhand smartphones. After his old dumbphone died a few months ago, Runyon picked up a used iPhone. He just needed it for basic phone capabilities, and used it as such, turning data off. However, AT&T eventually figured out he was making calls from a smartphone, and they decided he needed a data plan, even if he wasn't going to use it. They went ahead and opted him into a plan that cost an extra $30 a month. Quoting: 'According to AT&T: They can opt me into a contract that I didn't agree to because I was using a phone that I didn't buy from them because it had the ability to use data that I wasn't using (and was turned off). To top it all off, they got the privilege of charging me for it because I bought a differently categorized device – even though the actual usage of their network did not change at all and I never reconstituted a new agreement with them.'"