Same problem on Android 4.4.2 with latest textra version. Mobile Data does not turn off automatically after using MMS. Samsung galaxy s3 rooted, Textra 4.22. On old versions of textra this was never a problem. Now mobile data stays on and has to be manually turned off again.

You can find more explanation at https://chuonglepham.wordpress.com/2017/10/07/android-setmobiledataenabled-method/. Simply put: Google et al do not want mobile network to be switched off so they can 1) data mining, 2) force crappy ads down your throat, and 3) cost you money when you exceed your data limit for your mobile plan.

The only way to go is root your mobile device and use the method found in the above link. You can create a widget for yourself with the Java codes provided in the link.

I found sollution for device which has root:
http://stackoverflow.com/questions/26539445/the-setmobiledataenabled-method-is-no-longer-callable-as-of-android-l-and-later

Check command svc data enable and svc data disable

I noticed that on/off mobile data is not work properly when I send photos directly from the gallery. Then the mobile data will remain ON after sending MMS.

Yeah, that's the same for me, and I have a Samsung Galaxy Stratosphere II.

I don't like how it doesn't shut it off because it's very misleading. The description of this feature under Settings says TEMPORARILY activate mobile data. That implies that it shuts it off afterwards.

yes! and auto data on off for mms