Here we call it Orange card(which I use), Tricom Amigo, Codetel has a card, and I think Centennial might too.
You buy a card for 100 or so pesos at a kiosk or store and when it is gone, you can be called for up to a month or so, but you can't call anymore. My Orange works fine for me here in SD. I want a Tricom phone with a regular billed plan also, but maybe next Christmas, ehh?