I feel this may be hopeless after reading thread upon thread of people complaining about the same thing. My iphone 5 data is nearly useless in most buildings including my own apartment. However when I step outside it usually picks it back up, however this is not always the case. When it switches to 3G it typically will not load anything and usually turns into an "o" and displays the cannot activate cellular data network error. My zipcode is 22801. I think it's time sprint started giving people an actual explanation as to the cause of this problem rather than just responding with a cheerful, "I'll be happy to look into it for you". I am honestly considering ponying up the cash for the early termination fee and going back to pre paid service as this is wasting my money. Looking forward to hearing more than one of the robotic responses that sprint reps have been replying to most everyone else's threads with!
I've been having the exact same issue since yesterday -- I used to be able to stream music from my phone in my office building (14841 Dallas Pkwy #125 Dallas, TX 75254) but I can't even send or receive texts...at one point I had no bars at all.
I noticed something changed with my wifi hotspot tethering options yesterday, but that's it.