Go to settings and select messages, and make sure mms messaging is turned on. I was having that trouble and that was the problem. I hope this fixes your problem.
I am unable to send or recieve MMS messages through my Iphone to other carriers. Anyone else having problems or know of a solution?
Thanks for your feedback. Adding to the suggestion provided, perhaps you can power cycle your device to see if it refreshes your connection. Afterward retry sending a MMS message. Also, ask someone to try and send you a MMS message. Please make sure that the once your sending the MMS message has a device able to receive a MMS message and that they have not blocked their phone from receiving MMS messages.
I recommend resetting your phone. This reset will not erase any of your personal data. Please use the reset instructions that I have highlighted in red. You can also find these and other instructions in your online manual. I have provided a link to your manual below:
Reset all settings: Choose General > Reset and tap Reset All Settings.
All your preferences and settings are reset. Information (such as contacts and calendars) and media (such as songs and videos) aren’t affected.
Erase all content and settings: Connect iPhone to your computer or a power adapter. Choose General > Reset and tap “Erase All Content and Settings.”
This resets all settings, and erases all your information and media by removing the encryption key to the data (which is encrypted using 256-bit AES encryption).
Reset network settings: Choose General > Reset and tap Reset Network Settings.
When you reset network settings, your list of previously used networks and VPN settings not installed by a configuration profile are removed. Wi-Fi is turned off and then back on, disconnecting you from any network you’re on. The Wi-Fi and “Ask to Join Networks” settings are left turned on.
Are you still having this issue? If so, it may be a provisioning issue. May I ask you to send me a private message with your mobile number and a contact number so I can investigate this issue. Please refer to this message when to send me a PM.