Uh oh. Nokia’s Lumia 900 is currently AT&T’s flagship “hero” device but new owners are already expressing concerns over the phone’s ability to maintain a data connection. Reportedly, the phone has had trouble staying connected to HSPA and LTE data networks, so users aren’t able to surf the web or download any data. AT&T is reportedly telling Lumia 900 owners to pull their SIM card, restart the phone or even perform a master reset — all things you don’t regularly expect to have to do with a new phone. The good news is that several users have reported that at least one of those steps helped solve the problem, and we’re betting it’s most likely a SIM provisioning issue since we haven’t had any issues on two in-house units. Did you buy a Lumia 900 from AT&T? Have you had any issues?