Sorry for the inconvenience. Make sure that you have 3G service on your phone display so as to make sure you're in Sprint coverage/service. If you don’t see 3g service on your phone turn off Wi-Fi, turn off your phone and then reset Network Settings (From the Home screen, tap Settings/In Settings, tap General/In General Settings, scroll up and tap Reset/In Reset, tap Reset Network Settings/Tap Reset Network Settings/The iPhone will power cycle and restore Network Settings).Check if your phone can be activated through Sprint Network.
Other options would be to activate iPhone 4S is through WIFI or iTunes.
Sprint S.M.A.R.T Agents Sprint S.M.A.R.T Agent are here to help Monday through Friday 6:00 AM CT - 6:00 PM CT. If you need to speak to an agent outside of these hours, please visit Sprint Chat