iPod touch Peel 520 2nd Version for ipod touch 4 ? free call sim

I think you still need to buy a contract from the carrier that sells the Peel.

which carrier do you need to use the Peel 520? I use Sprint, looks like the sim for Peel 520 is GSM! Is that correct? Can I not use this with Sprint?

Does any carrier in US support Peel 520? I see that the first version was supported by virgin via sprint.

gsm

the peel uses GSM = ATT, T Mobile

If you already have a plan, drop your sim from the old phone into the peel. if not get a contract or buy a prepaid sim.