How does iOS handle data usage when receiving SMS/MMS

8.0.2 says it fixes a big when it was handling cellular data usage when dealing with MMS/SMS.

What was it doing before and what is it supposed to be doing?

If I send a message with a video attached or a picture through the carrier (not iMessage) does this count against my data usage or is it included in Unlimited text messaging? What about if I am connected to WiFi at the time?

 

I don't know how Apple has done it, and what it changed, but it could be a problem where they load too much data when downloading the data in the MMS from the MMSC server.

MMS works like an e-mail. When you send an MMS, you're sending a MIME e-mail to the recipient's carrier. That carrier stores the data on their MMSC server and sends a special MMS to the recipient containing the URL of the MMS on the MMSC. The recipient's phone then triggers their WAP browser, and downloads it over GPRS.

Due to the old-school nature of MMS, you cannot send/receive via WiFi.

Whether you can do it for free depends on your subscription. Most subscriptions have "Free SMS & MMS".