So basically I can't send SMS or MMS. It used to work perfectly fine but for some reason it's stopped. I can receive SMS but can't respond. Whenever I try to send a MMS it says something like "can't send unsupported format" I have literally tried everything I can find on the internet short of a factory reset, so I decided to see if anyone here was experiencing this or has a fix.
completely understandable that you don't want to Factory Reset, setting up the device again is annoying even if a lot of the data does get restored...
It may be something the carrier could help with if you haven't spoken to them already. Or it could be software issue which samsung techs can help with... which you can submit an error report to Samsung Members after reproducing the issue.
Please share your device's model number, carrier, and software version, the messages app version would also be helpful.