Why can I receive texts over WiFi from people who aren't on iOS?

[deckeda]

Someone who I know, who uses an Android phone just texted me. I received it over WiFi --- I think --- because there's no AT&T here. But the phone keeps looking for service because it's not in AirPlane mode --- I want to retain WiFi. Did it "roam" just long enough to receive the message over cellular? I certainly can't text back.

[rgG]

Must have roamed or picked up a signal just long enough to get the text, cause unless you are using something like iMessage or GChat, you can't text over wifi.

[space-time]

There are some apps to send "free" SMS, I think those work via WiFi