How do disable cell phone signal Iphone 4

how can I disable cell signal on Iphone 4. Friend gave me his phone I want to use it as mp3 player how can I disable cell signal I did a restore but still connects to sprint and gives me his old number?
Answer #1
Take the SIM out of it ?
Answer #2
if you just going to use it as a MP3 player then take the sim out and it will no longer have any cell signal.
Answer #3
Not sure of that one has a iPhone data radio switch – turn that off, or use Airplane mode, that will switch all signals off.
Answer #4
Its a CDMA phone I guess airplane mode does it