I also have AT&T DSL & Landline phone. I watch very little TV, and that is OTA. I do spend hours a day on the internet using a variety of PCs and a smartphone I just activated last month. Some days I download 4 GB of material, mostly operating systems, a hobby of mine. I suspect that overall I use far more per month than the low amount of data available for a basic smartphone, so haven't yet jettisoned the DSL.
Got my smartphone (Samsung Galaxy something )from Target for $45 net, and transferred my unused Tracfone time to it, for no charge at all. So until I use up one of my 3 baskets of smartphone usage, I stand to pay nothing until next September.