MMS not working (galaxy note 9)

Hello MH_Dani, we would be more than happy to investigate your issue regarding being unable to send MMS messages and encountering network errors.

We can certainly understand how frustrating this must be in the mean time, and we want to ensure we are getting to the bottom of the issue. To aid us in our investigation, please may you verify and answer the following questions:

• Have you completed all steps from our Troubleshoot and Resolve page? ( If you have already gone through this, no worries we will move forward.)
• Have you recently switched from an iPhone to an Android device prior to this issue.
• Have you factory reset your device?
• Have you tried taking out the sim card and making sure it is secure within the sim card tray? 
• Are you able to make and receive phone calls?

We look forward to hearing from you soon. 

Thank you for visiting AT&T Community Forums!

Carlton, AT&T Community Specialist