Straight talk is a cellular reseller. They used to operate on both att and T-Mobile networks, but recently stopped offering Sim cards on the att network. The home phone service they now offer is basically a cell unit that you plug your regular phone into. You can port and keep your current number. I know all this because my wife and I recently moved to smart phones. We bought unlocked Google/lg nexus phones and dropped expensive att for reseller Sims which saves us a ton of money. In the process I experimented for a month on a straight talk T-Mobile Sim followed by a month on a att net 10 Sim. We ultimately went with net 10 on the att network for better data speeds. We've considered moving our home land line to either net 10 or straight talk but haven't done so because we do like having a hard wire back up for emergencies and for the better sound quality. Hope this helps.