mms - please help me or am I going mad!!

[J-A-B]

I have a new Sony Z3, I always had Sony/Sony Ericsson for the last 15 year!!

Anyway here's my problem, I have always been able to send an mms without having to manually turn the mobile data on and off but with this phone I do! Is it the phone or the settings?  I'm told by o2 quite catagorically that I have never been able to send or recieve a picture message without having to MANUALLY turn my mobile data on and off - I think I know what I've been doing for the last umpteen years, but I was more or less told I'm making it up which has made me quite angry with them cos I can happily put the sim card back in my old phone and do it!!! I have a picture message bolt on so I could just happily continue to send my picture texts anytime and carefree as in the past without having to do anything but press send on my messaging app - although of course according to o2 this was just a daydream I've been having for numerous years.  Please someone tell me I'm not going mad and am I missing some setting or something.  In hope for my sanity. 

[MI5]

Sounds more like an error in Sony's coding rather than a deliberate decision?

[viridis]

That's what I was thinking but appears on rom variations of quite a few different manufacturers handsets.

[MI5]

Other thoughts are that it is deliberate to prevent data leaks when roaming and receiving an incoming MMS....
Must be a rationale for it somewhere