Try resetting your MMS settings, What phone have you got?
Further to Dazm33's advice, the advice usually given for setting up MMS is to attempt to send a picture to your own number.
Welcome to the community and thanks for posting. I'm terribly sorry you're unable to send picture messages.
I just want to clear a few things up. Could you please answer the following:-
Can you send a picture message to your own number?
Are these still failing to other numbers?
What else was discussed when you called us?
I hope to hear from you soon.