How did you solve this issue? or did it just resolved on its own?
This exact same thing is happening to me right now.
I can receive MMS but cannot sent it and get in red "Message not sent: service not activated on network".
I have not touched any APN settings and just yesterday I was sending MMS just fine.
I dialed #*#4636 #*# and the SMSC was blank so I hit "refresh" and this # came up 19703769830 then I hit update and nothing happens but that # remains.
On this thread I'm not sure I read what the solution was.
