Always expect prorated charges when signing up for new cellular service, but I would also keep an eye out for $40 activation fees. I know that whenever I got my gf an iPhone before we flew out to Vegas last summer, AT&T tried to charge us a activation fee even though I was bringing my own device and she was using AT&T Next. They claimed it was a system issue, but system issue or not, it still is something to keep an eye out for. From the sounds of it I wouldn't doubt you had around $20 in proration (which is average) and prob got charged the activation fees!