My Lumia 1020 won't send text messages

[Jadesong]

After spending over two hours with an ATT tech on the phone, still haven't been able to resolve my issue. I can send texts, but not with an attachment. Can't send pictures. Started this morning, and phone, Lumia 1020 was updated to Windows10 over the Christmas holidays by techie grandchild. Worked okay till this morning. Any help or suggestions, most appreciated. Grandma D.