Can't receive pictures if cellular data is turned off AT&T?

I mainly use Wi-Fi as my data so I turn my cellular data off. When it's turn off I don't receive picture message from another non iphone user, like I receive picture messages from iMessage not from regular text message.

Picture messages are sent via MMS which uses the carrier's data plan.

MMS uses data which should be obvious because it doesn't work when you have data off.