help getting a dta

I was told by a comcast rep via an online chat that I could get a dta box for my television without a cable box where I only receive basic channels. I was told I needed to call. I did call and the intiial rep had absolutely no idea what i was talking about. He researched it and transfered me to a special unit handling this issue. that gentleman attempted to help me but said the service had not yet been rolled out in my area - clearly it has been based on some research i did yoday. I live in Boston. How do I get a DTA box?